British police will travel outside of the UK as part of their investigation into the death of former Russian spy Alexander Litvinenko, the government has confirmed.
The ex-KGB agent died on November 23rd in London from radiation poisoning. After his death, he was found to have significant amounts of radioactive isotope polonium-210 (po-210) in his body.
A number of sites and people Mr Litvinenko came into contact with are being monitored by both police and health officials, although the Health Protection Agency is emphasising the threat to public health is low.
And today home secretary John Reid said: "Over the next few days I think that all of these things will widen out a little from the circle just being here in Britain.
"Tomorrow I will be at the European council and I will certainly be sharing information and getting what we can from European counterparts."
Mr Litvinenko, 43, was a vocal critic of Russian president Vladimir Putin and claimed on his deathbed that the Kremlin was responsible for his killing. It has denied any involvement, and Mr Reid refused to be drawn on rumours.
"The worst thing we can do is speculate. We will end up with egg on our face. This isn't a game of Cluedo," he told Sky News' Sunday Live programme.
The home secretary reiterated that members of the public should not be overly worried by ongoing investigations into possible radioactive contamination.
"If I thought there was any risk to people arising out of some of these contamination sites we would immediately put that out," he added.
Yesterday tests showed that a close contact of Mr Litvinenko displayed no "evidence of radiation toxicity".
Italian professor Mario Scaramella was one of the last people to see Mr Litvinenko, who took British citizenship two months ago, before he fell ill when they met for lunch at a central London restaurant in early November.
But staff at University College Hospital, where the ex-KGB agent died, say that Mr Scaramella is doing well despite previously testing positive for po-210.