By JILL LAWLESS and DANICA KIRKA
LONDON (AP) — British police asked the military on Friday to help investigate the nerve-agent poisoning of a former spy, as investigators' attention increasingly focused on the victim's house in a quiet suburban street.
Meanwhile, Russia's foreign minister said his country might be willing to help with this investigation, but expressed resentment at suggestions Moscow was behind the attack on Sergei Skripal. The ex-agent was found unconscious on a bench in the English city of Salisbury on Sunday alongside his daughter Yulia.
The pair are in a critical condition in a local hospital. A police officer who helped investigate is in serious condition, and a total of 21 people have received medical treatment.
Counterterrorism detectives have called in military help "to remove a number of vehicles and objects from the scene" of the attack, the Metropolitan Police force said.
About 180 soldiers, marines and air force personnel have been called in because "they have the necessary capability and expertise," police said. They said health advice remains the same — that there is no broader risk to the public.
Detectives are retracing the movements of Sergei and Yulia Skripal as they try to discover how the toxin was administered and where it was manufactured. British authorities have not disclosed what nerve agent was involved.
Police have cordoned off sites including Skripal's house, a car, the cemetery where his wife is buried, a restaurant and a pub.
Former London police chief Ian Blair said Friday that a police officer who is in serious condition visited Skripal's house — perhaps a hint that the nerve agent may have been delivered there.
Blair told BBC radio that Det. Sgt. Nick Bailey "has actually been to the house, whereas there is a doctor who looked after the patients in the open who hasn't been affected at all. There may be some clues floating around in here."
Highly toxic and banned in almost all countries, nerve agents require expertise to manufacture — leading some to suspect whoever poisoned Skripal had the backing of a state.
"A well-equipped lab and a very experienced analytical chemist can do it, but it's not the sort of thing a chancer doing kitchen-sink chemistry can get away with," said chemical weapons expert Richard Guthrie.
Skripal, a former Russian military intelligence officer, was convicted in his home country in 2006 of spying for Britain and released in 2010 as part of a spy swap. He had been living quietly in Salisbury, a cathedral city 90 miles (140 kilometers) southwest of London.
Russian Foreign Minister Sergey Lavrov said Moscow was "ready to consider" lending a hand, "whether it's poisoning of some British subjects, whether it's rumors about interference in the U.S. election campaign."
"But in order to conduct such cases, it is necessary not to immediately run out on TV screens with unfounded allegations," Lavrov was quoted as saying by Russian state news agency Tass in the Ethiopian capital, Addis Ababa.
The U.K. has vowed to take strong action against whoever was responsible for the "brazen and reckless" attack.
British authorities say it's too soon to lay blame, but suspicions have fallen on Russia.
Those branded enemies of the Russian state have sometimes died mysteriously abroad, and the Skripal case echoes the death of Alexander Litvinenko, a former Russian agent who was poisoned in London in 2006 with radioactive polonium-210.
A British public inquiry found that Russia was responsible for Litvinenko's killing, and that Russian President Vladimir Putin probably approved it.
Blair, the former London police chief, called for a review of the deaths of 14 Russians in the U.K. amid suggestions they were targeted by the Russian state.
Blair, who led the London force when Litvinenko was fatally poisoned, told the BBC it is important to find out "whether there is some pattern here."
A BuzzFeed News investigation claimed U.S. spy agencies have linked 14 deaths to Russia, but U.K. police shut down the cases.
Russian media have mocked suggestions of Moscow involvement in the Skripal attack — but also noted that those who betray Russia seem to come to a bad end.
One anchorman on a Russian state television news show began a report on Skripal's poisoning with a warning to anyone considering becoming a double agent.
Channel One anchorman Kirill Kleimenov said in the Wednesday broadcast that he didn't wish death or suffering on anyone but wanted those "who dream of such a career" to know that traitors rarely live long.
"Alcoholism, drug addiction, stress and depression are inevitable professional illnesses of a traitor, resulting in heart attacks and even suicide," Kleimenov said.
Jim Heintz in Moscow contributed to this story.
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