Britain, US intercepted 'chatter' supporting theory bomb took down Russian jet - officials

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Security Tightened at Egypt Airport Amid Bomb Theory

British and U.S. spies intercepted "chatter" from suspected militants and at least one other government suggesting that a bomb, possibly hidden in luggage in the hold, downed a Russian airliner on Saturday, killing all 224 people on board, Western intelligence sources said.

Prime Minister David Cameron halted flights to and from Sharm al-Sheikh on Wednesday after intelligence shown to him indicated that it was likely that the Airbus A321 heading towards St Petersburg was brought down by a bomb.

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Britain says there was a "credible threat" but has refused to comment further on the intelligence involved, citing long-standing rules about disclosing operational details about live investigations.

Western intelligence sources said some of the assessment about the bomb came from intercepted communications both from suspected militants and from one or more governments involved in the investigation.

The intelligence sources, who spoke on condition of anonymity due to the sensitivity of the situation, said the evidence was not categorical and that there is still no hard forensic or scientific evidence to support the bomb theory.

"We still cannot be categorical but there is a distinct and credible possibility that there was a bomb," one source said.

See more of the crash and its aftermath:

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Russian plane crash in Egypt wreckage and aftermath
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Britain, US intercepted 'chatter' supporting theory bomb took down Russian jet - officials
Debris belonging to the A321 Russian airliner are seen at the site of the crash in Wadi el-Zolmat, a mountainous area in Egypt's Sinai Peninsula on November 1, 2015. International investigators began probing why a Russian airliner carrying 224 people crashed in Egypt's Sinai Peninsula, killing everyone on board, as rescue workers widened their search for missing victims. AFP PHOTO / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
SUEZ, EGYPT - NOVEMBER 01: A plane part is seen as the Egyptian officials inspect the crash site of Russian Airliner in Suez, Egypt on November 01, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on yesterday. According to Egypts Civil Aviation Authority, the plane had been lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Alaa El Kassas/Anadolu Agency/Getty Images)
Debris of the A321 Russian airliner lie on the ground a day after the plane crashed in Wadi al-Zolomat, a mountainous area in Egypt's Sinai Peninsula, on November 1, 2015. International investigators began probing why the Russian airliner carrying 224 people crashed in the Sinai Peninsula, killing everyone on board, as rescue workers widened their search for missing victims. AFP PHOTO / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
Debris of the A321 Russian airliner lie on the ground a day after the plane crashed in Wadi al-Zolomat, a mountainous area in Egypt's Sinai Peninsula, on November 1, 2015. International investigators began probing why the Russian airliner carrying 224 people crashed in the Sinai Peninsula, killing everyone on board, as rescue workers widened their search for missing victims. AFP PHOTO / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
SUEZ, EGYPT - NOVEMBER 01: Egyptian officials inspect the crash site of Russian Airliner in Suez, Egypt on November 01, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on yesterday. According to Egypts Civil Aviation Authority, the plane had been lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Alaa El Kassas/Anadolu Agency/Getty Images)
SUEZ, EGYPT - NOVEMBER 01: Egyptian officials inspect the crash site of Russian Airliner in Suez, Egypt on November 01, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on yesterday. According to Egypts Civil Aviation Authority, the plane had been lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Alaa El Kassas/Anadolu Agency/Getty Images)
CAIRO, EGYPT - OCTOBER 31: Ambulances bring the bodies of the victims found at crash site of Russian Airliner, at Zinhoum Hospital's Morgue in Cairo, Egypt on October 31, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on Saturday, according to the Egyptian Prime Minister's office. According to Egypts Civil Aviation Authority, the plane lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Ibrahim Ramadan/Anadolu Agency/Getty Images)
CAIRO, EGYPT - OCTOBER 31: Ambulances bring the bodies of the victims found at crash site of Russian Airliner, at Zinhoum Hospital's Morgue in Cairo, Egypt on October 31, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on Saturday, according to the Egyptian Prime Minister's office. According to Egypts Civil Aviation Authority, the plane lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Ibrahim Ramadan/Anadolu Agency/Getty Images)
CAIRO, EGYPT - OCTOBER 31: Ambulances bring the bodies of the victims found at crash site of Russian Airliner, at Zinhoum Hospital's Morgue in Cairo, Egypt on October 31, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on Saturday, according to the Egyptian Prime Minister's office. According to Egypts Civil Aviation Authority, the plane lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Ibrahim Ramadan/Anadolu Agency/Getty Images)
CAIRO, EGYPT - OCTOBER 31: Ambulances bring the bodies of the victims found at crash site of Russian Airliner, at Zinhoum Hospital's Morgue in Cairo, Egypt on October 31, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on Saturday, according to the Egyptian Prime Minister's office. According to Egypts Civil Aviation Authority, the plane lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Ibrahim Ramadan/Anadolu Agency/Getty Images)
Egyptian ambulance arrives to Kabret military air base by the Suez Canal on October 31, 2015, after victims of a Russian airliner that crashed in the Sinai Peninsula were brought to the base before being transported to a morgue. Egypt's government said 15 bodies have been recovered and transferred to a morgue so far from the site of the crash. AFP PHOTO / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
Egyptian paramedics load the corpses of Russian victims of a Russian passenger plane crash in the Sinai Peninsula, into a military plane at Kabret military air base by the Suez Canal on October 31, 2015. Egypt's government said 15 bodies have been recovered and transferred to a morgue so far from the site of the crash. AFP PHOTO / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
SUEZ, EGYPT - OCTOBER 31: Egyptian officials receives the corpses of 34 passengers, found at crash site of Russian Airliner, at Kabret Military Base in Suez, Egypt on October 31, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on Saturday, according to the Egyptian Prime Minister's office. According to Egypts Civil Aviation Authority, the plane lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Mostafa El Shemy/Anadolu Agency/Getty Images)
Egyptian ambulances line up at Kabret military air base by the Suez Canal on October 31, 2015, after victims of a Russian airliner that crashed in the Sinai Peninsula were brought to the base before being transported to a morgue. Egypt's government said 15 bodies have been recovered and transferred to a morgue so far from the site of the crash. AFP PHOTO / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
An Egyptian ambulance waits at Kabret military air base by the Suez Canal on October 31, 2015, after victims of a Russian airliner that crashed in the Sinai Peninsula were brought to the base before being transported to a morgue. Egypt's government said 15 bodies have been recovered and transferred to a morgue so far from the site of the crash. AFP PHOTO / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
SUEZ, EGYPT - OCTOBER 31: Egyptian officials receives the corpses of 34 passengers, found at crash site of Russian Airliner, at Kabret Military Base in Suez, Egypt on October 31, 2015. A Russian Airbus-321 airliner with 224 people aboard crashed in Egypt's Sinai Peninsula on Saturday, according to the Egyptian Prime Minister's office. According to Egypts Civil Aviation Authority, the plane lost contact with air-traffic controllers shortly after taking off from the Egyptian Red Sea resort city of Sharm el-Sheikh en route to St Petersburg. (Photo by Alaa El Kassas/Anadolu Agency/Getty Images)
Egyptian ambulances carrying the corpses of Russian victims of a Russian passenger plane crash in the Sinai Peninsula, off load the bodies into a military aircraft at Kabret military air base by the Suez Canal on October 31, 2015. Egypt's government said 15 bodies have been recovered and transferred to a morgue so far from the site of the crash. AFP PHOTO / KHALED DESOUKI (Photo credit should read KHALED DESOUKI/AFP/Getty Images)
Egyptian police officers stand guard outside the Zeinhom Morgue in Cairo on October 31, 2015, as they wait for the victims of the Russian charter plane. A Russian plane carrying 224 people crashed in a mountainous part of Egypt's Sinai Peninsula, killing everyone on board, officials said. AFP PHOTO /MOHAMED EL-SHAHED (Photo credit should read MOHAMED EL-SHAHED/AFP/Getty Images)
Egyptian police officers stand guard, next to graffiti condemning police brutality, outside the Zeinhom Morgue in Cairo on October 31, 2015, as they wait for the victims of the Russian charter plane. A Russian plane carrying 224 people crashed in a mountainous part of Egypt's Sinai Peninsula, killing everyone on board, officials said. AFP PHOTO /MOHAMED EL-SHAHED (Photo credit should read MOHAMED EL-SHAHED/AFP/Getty Images)
Egyptian police officers stand guard outside the Zeinhom Morgue in Cairo on October 31, 2015, as they wait for the victims of the Russian charter plane. A Russian plane carrying 224 people crashed in a mountainous part of Egypt's Sinai Peninsula, killing everyone on board, officials said. AFP PHOTO /MOHAMED EL-SHAHED (Photo credit should read MOHAMED EL-SHAHED/AFP/Getty Images)
Egyptian police officers stand guard outside the Zeinhom Morgue in Cairo on October 31, 2015, as they wait for the victims of the Russian charter plane. A Russian plane carrying 224 people crashed in a mountainous part of Egypt's Sinai Peninsula, killing everyone on board, officials said. AFP PHOTO /MOHAMED EL-SHAHED (Photo credit should read MOHAMED EL-SHAHED/AFP/Getty Images)
Egyptian police officers stand guard outside the Zeinhom Morgue in Cairo on October 31, 2015, as they wait for the victims of the Russian charter plane. A Russian plane carrying 224 people crashed in a mountainous part of Egypt's Sinai Peninsula, killing everyone on board, officials said. AFP PHOTO /MOHAMED EL-SHAHED (Photo credit should read MOHAMED EL-SHAHED/AFP/Getty Images)
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Two sources with knowledge of the matter said the bomb may have been hidden in luggage in the hold of the Russian plane. They refused to give any further information.

A U.S. official said the "chatter" intercepted about the bomb includes conflicting details about whether the bomb was placed on the plane.

Russia, which was initially critical of Britain's assessment of what it has called a crash, on Friday suspended all flights to Egypt.

President Vladimir Putin ordered the halt to flights after Alexander Bortnikov, the head of Russia's FSB security service, recommended that Russia suspend all passenger flights to Egypt until it knew exactly what caused the crash.

"Until we know the real reasons for what happened, I consider it expedient to stop Russian flights to Egypt," said Bortnikov. "Above all, this concerns tourist routes."

Cameron's spokesman declined to be drawn on details.

"The evidence we received suggested there was a credible threat with regard to Sharm al-Sheikh airport which is why we have taken the actions we have."

"I am not going to get into discussions on security matters. I am not going to speculate on the intelligence."

(Editing by Tim Ahmann and Giles Elgood)

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Notable plane crashes in recent years
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Britain, US intercepted 'chatter' supporting theory bomb took down Russian jet - officials
A photo taken on July 23, 2014 shows the crash site of the downed Malaysia Airlines flight MH17, in a field near the village of Grabove, in the Donetsk region. The first bodies from flight MH17 arrived in the Netherlands on July 23 almost a week after it was shot down over Ukraine, with grieving relatives and the king and queen solemnly receiving the as yet unidentified victims. AFP PHOTO/ BULENT KILIC (Photo credit should read BULENT KILIC/AFP/Getty Images)
Firefighters (L) inspect a house damaged by fire caused after a light plane crashed into a residential area in Tokyo on July 26, 2015. The light single-engine plane crashed into a residential area in Tokyo, setting fire to several houses and reportedly killing three people. JAPAN OUT -- AFP PHOTO / JIJI PRESS (Photo credit should read JIJI PRESS/AFP/Getty Images)
VENICE, CA - MARCH 05: A general view at the Penmar Golf Course after a single-engine plane piloted by actor Harrison Ford crashed on March 5, 2015 in Venice, California. Ford was reportedly taken to a nearby hospital in fair to moderate condition. (Photo by Albert L. Ortega/Getty Images)
Iranian security forces react next to the remains of a plane as they secure the scene of a crash near Tehran's Mehrabad airport on August 10, 2014. A civilian airliner crashed on take-off near the Mehrabad airport in the capital, Iranian news agencies said, with reports that almost 50 people were killed. AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images)
GAITHERSBURG, MD - DEC 08: Three people were killed in this house after it caught fire due to a plane that crashed just yards away. A plane crashed into houses on Drop Forge Lane in Gaithersburg, Maryland today. Three persons were killed in the plane and 3 persons were killed in one of the homes. (Photo by Michael S. Williamson/The Washington Post via Getty Images
Indonesian rescuers search through wreckage of the Trigana Air ATR 42-300 twin-turboprop plane at the crash site in the mountainous area of Oksibil on August 18, 2015. A plane that crashed in eastern Indonesia was found on August 18 'completely destroyed' with the bodies of all 54 passengers and crew strewn amid the wreckage in a fire-blackened jungle clearing, officials said. AFP PHOTO (Photo credit should read STR/AFP/Getty Images)
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