British media said earlier that polonium-210, a toxic uranium by-product discovered in the body of Alexander Litvinienko who died last Thursday, could have been produced at a chemicals company in the city of Zheleznogorsk in the Krasnoyarsk Territory, which produces weapons-grade plutonium.
Company managers said Po-210 has never been part of the production cycles at any of the local companies.
Commenting on the UK media theory, Viktor Mikhailov, director of the Russian Institute of Strategic Stability, said experts could not possibly have identified the origin of the radioactive isotope so quickly, although it is in principle possible to pinpoint the facility where a given sample of Po-210 is produced.
Russian security defector Litvinenko, an outspoken critic of President Vladimir Putin's administration and a close associate of exiled oligarch Boris Berezovsky, died in a London hospital with symptoms of radioactive poisoning. British health officials said a large dose of Po-210 was found in his body.
British Airways announced Wednesday that low levels of radioactive contamination had been detected on two of their planes that traveled the Moscow-London route, and that the airliners have been grounded at London's Heathrow Airport.
Following Litvinenko's death, the Western press circulated a message purporting to be his deathbed note, in which he accused Putin of orchestrating his death, an allegation the president dismissed.
