UK police looking at 240 pieces of evidence in nerve agent attack - minister

SALISBURY, England, March 10 (Reuters) - British police have identified more than 200 witnesses and are looking at more than 240 pieces of evidence in their investigation into a nerve agent attack on a Russian ex-spy and his daughter, interior minister Amber Rudd said on Saturday.

Former double agent Sergei Skripal, 66, and his daughter Yulia, 33, have been in hospital in a critical condition since Sunday, when they were found unconscious on a bench in the southern English cathedral city of Salisbury.

"The two victims remain in hospital and they're critical but stable," Rudd told reporters after chairing a meeting of the government's Cobra security committee.

She also said that Nick Bailey, a police officer who became unwell after taking part in the response to the attack, remained seriously ill but was talking and engaging with his family.

Rudd said more than 250 counter terrorism police were involved in the investigation, which was proceeding with "speed and professionalism."

Many in British media and politics have speculated that Russia could have played a part in the attack on Skripal, but Rudd reiterated that it was too early to say who was responsible, and police should be given the time and space to determine the facts.

In Salisbury, normally a quiet city, military vehicles and troops in protective suits and gas masks were seen working at several of the sites associated with the Skripal investigation.

At an ambulance station a short distance from the city center, troops in light grey overalls and gas masks covered an ambulance with a black tarpaulin, while at the hospital where the Skripals were being treated another team used an army truck to remove a police car.

There was also a flurry of activity at the cemetery where Skripal's wife and son are buried, with forensic teams active in several parts of the site. Skripal's son, Alexander, died in July last year at the age of 43. British media reported that he died while in St Petersburg, Russia. Skripal's wife, Liudmila, died in 2012 of cancer at 60. (Reporting by Peter Nicholls in Salisbury and Estelle Shirbon in London Editing by Peter Graff)