Members of the public who visited areas frequented by the late Russian ex-spy Alexander Lit-vinenko shortly before he fell ill were asked to contact health authorities yesterday.
Traces of the radioactive material polonium 210 have been found at the Itsu sushi bar on Piccadilly and the Millennium Hotel in Grosvenor Square, both in central London, police said on Friday.
Britain's Health Protection Agency yesterday issued a statement asking anyone who visited the two locations on Nov. 1, the day Litvinenko fell ill, to contact the state-run National Health Service.
Britain's chief medical officer, Sir Liam Donaldson, is also issuing advice to doctors and hospitals on the risks and implications of being exposed to polonium 210, the statement said.
"We want to reassure the public that the risk of having been exposed to this substance remains low ... It can only represent a hazard if it is taken into the body -- by breathing it in, by taking it into the mouth or if it gets into a wound," the statement said.
Meanwhile, a top-level emergency planning committee featuring senior British ministers met yesterday as counter-terrorism police pieced together information about Litivinenko's death.
The COBRA committee, which handles the nation's response to crises, met earlier yesterday, a Cabinet Office spokeswoman said.
The committee features high-ranking ministers, police and intelligence chiefs and had previously met to discuss incidents including the July 7 suicide bombings in London last year.
British newspapers turned the spotlight yesterday on Russian President Vladimir Putin over the radiation poisoning death in London of one of his fiercest critics.
Some newspapers said the mystery surrounding the death of Litvinenko had echoes of the Cold War and potentially giant implications for Anglo-Russian relations.
Litvinenko accused Putin's regime of murder in a deathbead statement read out on Friday, less than 24 hours after his death in a London hospital.
The British government has already had words with the Russian ambassador.
The Guardian newspaper said senior British ministers were worried about a potential diplomatic fall-out with Russia.
It quoted one minister as saying that colleagues were "dreading" the prospect of a public inquest that could lead to embarrassing and lurid claims about Russia's alleged conduct.
The Daily Telegraph's editorial was entitled "The West is losing patience with Putin."
"If Mr Litvinenko was indeed assassinated on the orders of the Russian state, the consequences will be huge," it said.
"When one government deliberately uses lethal force in another's jurisdiction, it commits an act of terrorism -- arguably of war," it said.
The Times said Putin must prove by deeds that he was not linked to Litvinenko's death.
It said the former secret agent's final testament was "political dynamite."