Officials found traces of radiation on two British Airways jets, and the airline appealed Wednesday to tens of thousands of passengers who flew to Moscow or other cities to come forward - the latest twist in the inquiry into the poisoning death of a former Russian spy.
The airline said the "risk to public health is low," adding that it was in the process of contacting tens of thousands of passengers who flew on the jets.
Two planes at London's Heathrow Airport tested positive for traces of radiation and a third jet was taken out of service in Moscow awaiting examination, British Airways said.
Natalia Remnyova, administrator at Domodedovo Airport, the Moscow airport used by British Airways, said she knew nothing of a plane grounded there. Kremlin spokesman Dmitry Peskov said he could not comment because he had no information.
The airline said it was contacted by the British government Tuesday night and told to ground the jets and to let investigators looking into the death of former Russian spy Alexander Litvinenko test them for radiation.
High doses of polonium-210 - a rare radioactive element usually made in specialized nuclear facilities - were found in Litvinenko's body, and traces of radiation have been found at sites in London connected with the inquiry into his death.
All three planes had been on the London-Moscow route, British Airways said. In the last three weeks, the planes had also traveled routes across Europe. About 33,000 passengers had traveled on 221 flights on those planes, said Kate Gay, an airline spokeswoman.
Litvinenko, a former colonel with Russia's Federal Security Service - the successor agency to the KGB - had been a fierce critic of Russian President Vladimir Putin before his death from radiation poisoning on Nov. 23. From his deathbed, he blamed Putin for his poisoning. Putin has strongly denied the charge.
Meanwhile, Italian security expert Mario Scaramella, who was one of the last people to meet with Litvinenko before he fell ill, said tests cleared him of radioactive contamination.
The mysterious death has clouded Anglo-Russian relations. Prime Minister Tony Blair said police were determined to find out who was responsible for Litvinenko's death.
Traces of radiation have been found at six sites visited by Litvinenko.
Also Wednesday, it was announced former Prime Minister Yegor T. Gaidar, an architect of Russia's early post-Soviet market reforms, has been hospitalized with a mysterious illness that his daughter and associates said could have resulted from poisoning.
Gaidar, 50, fell ill in Ireland on Nov. 24, the day after Litvinenko died. Gaidar's spokesman, Valery A. Natarov, said Gaidar returned to Moscow on Nov. 26 and remained in a hospital.
Natarov said that Gaidar's condition had improved, but his illness had not been diagnosed .
Information from the New York Times was used in this report.