LONDON — At least six deaths were confirmed early Wednesday after a blaze ripped through a high-rise apartment block in the British capital as residents slept. At least 74 people were injured, according to authorities.
More than 250 firefighters battled the west London inferno through the night.
Local resident Tim Downie told NBC News he saw "people dangling children out the windows to try and get them to safety" as flames spread upward.
Witness Samira Lamrani said one woman wrapped a baby up "in some sort of thick blanket" and dropped the tot from around the 9th floor. "Miraculously the baby just sort of dropped in a straight line, and a guy just ran forward and the baby fell into his arms," she added.
Several others recounted watching people jumping from Grenfell Tower.
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Local officials believe that several hundred people were in the building, which dates back to the 1970s. The high-rise had a "stay put" policy in the event of a fire — with residents urged to shut their windows and doors and await rescue.
London Fire Brigade Commissioner Dany Cotton called it an "unprecedented incident," adding that a "number of fatalities" had been confirmed. Police later put the death toll at 6, but warned that figure was likely to grow.
"In my 29 years of being a firefighter, I have never, ever seen anything of this scale," Cotton said. "This is a major fire that's affected all floors of the 24-story structure from the second floor upwards."
She highlighted that "very large numbers" were rescued by emergency crews early on. But almost nine hours after the blaze broke out, Cotton admitted "we have absolutely no idea" how many people remained unaccounted for.
Michael Paramasivan was wearing only underwear and a robe when he fled the seventh floor about 35 minutes after the blaze was reported.
He described the scene in the stairwell as an "absolute horror story."
"There was smoke everywhere, people screaming and shouting," the 37-year-old told NBC News. "It all happened so fast but it was really, really frightening. I'm shaking."
He added: "They say you're supposed to put a towel under the door and wait for rescue but I wasn't going to hang around ... There was some kind of alarm but it was barely audible. It certainly wouldn't have woken you up."
Grenfell Tower has around 130 units. It is located about a mile northwest of Kensington Palace and is also near the Portobello Road market tourist attraction.
One dazed-looking man wearing a green bathrobe told reporters that he had "lost my wife on the staircase."
He added: "I don't know what happened to her. I'm trying to find out where she is."
James Wood, 32, who lives nearby, told NBC News he watched children "at the window screaming for help ... and the room eventually went up in flames."
Sajad Jamalvatan, a Grenfell Tower resident who was at the movies when the fire broke out, told NBC News that he "saw with my bare eyes someone jumping from the building."
The London Fire Brigade sent 40 vehicles to the scene after being called at 12:54 a.m. Wednesday local time (7:54 p.m. ET Tuesday). At least 20 patients were in critical condition, officials said.
By noon local time (7 a.m. ET), flames were still visible from some of the apartment block's windows.
Surrounding streets up to a mile away were covered in a layer of ash as a police helicopter buzzed over the area — an ethnically and economically diverse part of west London.
Ousama Itani, who lives nearby, told NBC News that one of his relatives heard people screaming from the building.
"We saw apartment after apartment getting lit up into flames," Itani added.
Nassima Boutrig, who lives opposite the tower, told the Associated Press that she heard people shouting: "Help, help, help."
She added: "The fire brigade could only help downstairs. It was fire up, up, up. They couldn't stop the fire."
Residents were hurrying along the streets trying to find news of neighbors or family members.
Kidan Opbekke, 39, was returning to her home in a nearby street after working a night shift when she saw the aftermath of the blaze.
"A friend of mine, from Eritrea, she cannot find her daughter," she sobbed in the street. "She got out from the fire but she cannot find her daughter."
Opbekke added: "This is terrible. There is nothing we can do except pray. We just came here to pray. And why, why did this happen?"
At the nearby Latymer Community Church, some of the shocked survivors were being given water and food. A local mosque also opened its doors.
"We will be providing temporary shelter and food for anyone of any faith or no faith affected by the fire," said Abdurahman Sayed, the head of the Al Manaar Mosque.
Authorities said the cause of the blaze remained unclear. Forensic investigators with cameras and protective suits were visible at the scene.
A structural engineer was sent to the scene to monitor whether the high-rise remained stable.
A newsletter distributed by Grenfell Tower's managers in May 2016 advised that "you are generally safest to stay put in your home to begin with; the fire brigade will arrive very quickly if a fire is reported."
It added that "smoke detection systems have been upgraded and extended" as part of a $12.8 million refurbishment project.
However, residents complained about fire safety standards in November — warning that only a serious blaze would make authorities listen.
Rydon, the firm which carried out the refurbishment, released a statement Wednesday saying its work "met all required building control, fire regulation and health and safety standards."
Alastair Jamieson, Chloe Hubbard, Mo Abbas, Will Clark, Emma Ong, Nick Bailey, F. Brinley Bruton, Rachel Elbaum, Sophie Harris, Tony Hemmings and Jason Cumming reported from London. Alex Johnson reported from Los Angeles. Erin Dean, E.D. Cauchi and Rima Abdelkader reported from New York. The Associated Press contributed to this report.