An investigation was under way on Saturday into Russia's black market trade in radioactive materials amid concern that quantities of polonium 210, the substance that killed former spy Alexander Litvinenko, are being stolen from nuclear sites.
Officials from Britain's Atomic Weapons Research Establishment and Porton Down, the government's Defense Science and Technology Laboratory were trying on Saturday to track down the precise source of the polonium 210 that was used in the murder of Litvinenko.
As British police drew up a list of witnesses for questioning over the death, experts warned that thefts from poorly protected nuclear facilities in the former Soviet Union were a major problem.
A senior source at the International Atomic Energy Agency (IAEA), said he had no doubt that the killing of Litvinenko was an "organized operation" which bore all the hallmarks of a foreign intelligence agency.
Theories that the death may have involved some form of state sponsorship were being investigated by MI5 and MI6 (British intelligence and counter intelligence) who are investigating the possibility that foreign agents may have been behind the death of Litvinenko.
A senior British security source said they were providing the police with material on "hostile intelligence agencies" operating in the UK, including those from Russia.
"Russia has never really decreased their activity in the UK from the end of the Cold War," he said.
More than anything, the death of the London-based former KGB spy has placed Russia's still thriving trade in radioactive material under scrutiny.
One of the few figures available, a database compiled by researchers at Stanford University in the US, revealed that about 40kg of weapons-usable uranium and plutonium were stolen from poorly protected nuclear facilities in the former Soviet Union between 1991 and 2002.
Although the IAEA has no confirmation of polonium finding its way in to the underground trade, there have been several unconfirmed reports of thefts.
In 1993 the Bulletin of Atomic Scientists reported that 10kg of polonium had disappeared from the Sarov, which produces the rare radioactive material and is described as Russia's own version of Los Alamos, the US government's nuclear research base in New Mexico.
Globally, there have been more than 300 cases during the past four years where individuals have been caught trying to smuggle radioactive material. Last year there were 103 confirmed incidents of trafficking and other unauthorized activities involving radioactive materials, many involving Russia.