LONDON (NYTIMES, WASHINGTON POST) - Britain authorities investigating the poisoning of a former Russian spy, Sergei V. Skripal, and his daughter visited the graves of Skripal's wife and son in the cathedral town of Salisbury, England, on Friday.
Dressed in large hazardous-material suits, the investigators began collecting evidence at Skripal's house in the town and erected a blue forensic tent around the grave of the son. The police said that they had requested military assistance to "remove a number of vehicles and objects from the scene". Skripal's wife, Lyudmila, 59, died in 2012 of uterine cancer, according to records from the National Health Service. His son Alexander, 43, died last year.
The authorities did not provide details, saying only that they had not exhumed any bodies, but the forensic activities at the London Road Cemetery intensified speculation about the poisonings.
Skripal, 66, and his daughter, Yulia S. Skripal, 33, were found unconscious Sunday afternoon on a bench outside a shopping centre in the southern English town.
The police later announced that the two had been poisoned with a nerve agent difficult to produce outside a government laboratory, heightening suspicions that Russia had played a role.
On Friday, army weapons experts and scores of troops were deployed to Salisbury to assist in the investigation. The 180 military personnel dispatched included the Royal Tank Regiment, Royal Marines, and chemical weapons specialists and bomb disposal units.
A day earlier, a presenter on Russia's Channel One news programme struck a different note, saying - without mentioning names - that the poisonings should serve as a warning to Russians considering betraying their country.
In 2006, Skripal was convicted in Russia of being a double agent and secretly passing classified information to British intelligence. In 2010, he was released from prison and sent to Britain as part of a spy exchange with Western agencies.
Skripal and his daughter remain in critical condition in Salisbury.
Much attention was focused Friday on Skripal's red brick home. Commentators said police were exploring the theory that the former Russian spy and his daughter, who was reportedly visiting from Moscow, were exposed to the nerve agent at the house.
A total of 21 people have received medical treatment after the mysterious attack, including Nick Bailey, a British police officer who is conscious but in serious condition.
Ian Blair, a former London police chief, told the BBC that Bailey had been to Skripal's home and had fallen ill, whereas a doctor who attended to the two Russians out in the open wasn't affected. "There may be some clues floating around in here," he said of Skripal's house.
During a visit to Salisbury on Friday, Amber Rudd, Britain's home secretary, warned against jumping to conclusions. "In terms of further options, that will have to wait until we're absolutely clear what the consequences could be and what the actual source of this nerve agent has been," Rudd said.
Police have not revealed what nerve agent was involved. But analysts say that if it is rare, it could help to narrow down which laboratory it was made in. "Identifying a rare nerve agent is like identifying exotic food on your plate," said Malcolm Sperrin, a medical physics expert. "If you are able to identify it, you might be able to say, 'Oh, this obviously comes from Harrods department store.' If it was a chicken pie you were looking at, well, that could have come from a million different places," he said.
Bob Seely, a Conservative lawmaker and member of the foreign affairs select committee, said the UK should be cautious about apportioning blame but said circumstantial evidence did raise suspicions of Russian involvement. "You don't get nerve agent down at the freezer of Morrisons," he told Sky News, referring to a British grocery store. "This comes from one or two places in the world, and one of them is the Russians."
The Kremlin, which denies any involvement, says it resents the finger-pointing and suspicions that Russia played a role. "We are accused of everything bad that happens in the world by our Western partners," Sergei Lavrov, Russia's foreign minister, said at a news conference Friday.