Two British Airways jets tested positive Wednesday for low-level radioactive contamination as the probe into the apparent murder of a former KGB agent uncovered a trail leading directly from London to Moscow.

FOX News has learned that British authorities are checking into whether anyone onboard the planes are associated with the radiation poisoning death of ex-Russian spy and Kremlin critic Alexander Litvinenko. Officials are planning to contact thousands of airplane passengers who flew on the jets.

Of the three Boeing 767s searched so far, low traces of radioactive material has been found on two of them.

Two planes at London's Heathrow Airport tested positive for traces of radiation, a third plane has been taken out of service in Moscow awaiting examination. The airline published the flights affected on its Web site.

Home Secretary John Reid disclosed the search following a meeting with COBRA, the government's emergency committee. Reid said two planes had been tested so far and that another would be.

The initial results of the forensic tests had shown very low traces of a radioactive substance onboard two aircraft, 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. Russian Transport Ministry and other government officials could not immediately be reached for comment.

British Airways said the investigation is confined to the three planes, which will remain out of service until further notice. British Airways was contacted Tuesday night by the government and told to ground the planes and allow investigators looking into Litvinenko's death to test them for radiation.

Litvinenko, who died Nov. 23 in a London hospital, claims Russian President Vladimir Putin was behind his death.

The former spy said he believed he had been poisoned on Nov. 1, while investigating the death of another Kremlin detractor investigative journalist Anna Politkovskaya. His hair fell out, his throat became swollen and his immune and nervous systems were severely damaged, he said.

London police say they are investigating the case as a "suspicious death" rather than murder, although they have devoted a large anti-terrorist force to the investigation.

Sky News reported Wednesday that authorities are interested in two Russian officials who met with Litvinenko on Nov. 1 and how they left the country. One is a former KGB agent.

All three planes had been on the London-Moscow route, British Airways said. In the last three weeks, the planes had also traveled to routes across Europe including Barcelona, Frankfurt and Athens. Around 30,000 passengers had traveled on 220 flights on those planes, said Kate Gay, an airline spokeswoman.

"British Airways understands that from advice it has been given that the risk to public health is low," the airline said in a statement. "The airline is in the process of making contact with customers who have traveled on flights operated by these aircraft, which operate within Europe."

High doses of polonium-210 — a rare radioactive element usually manufactured in specialized nuclear facilities — were found in Litvinenko's body, and traces of radiation have been found at sites in London connected with the investigation of his death.

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Meanwhile, Italian security expert Mario Scaramella, who was one of the last people to meet with Litvinenko before the former spy fell ill, said tests cleared him of radioactive contamination.

Scaramella came from Rome and met Litvinenko at a sushi bar in London on Nov. 1 — the day the former intelligence agent first reported the symptoms.

"I am fine," Scaramella told The Associated Press by telephone. "I am not contaminated and have not contaminated anybody else."

Scaramella returned to London to undergo tests and talk with the police Tuesday. He said he is in security protection and refused to say where he was.

More than three dozen staff at the two hospitals that treated Litvinenko will be tested for radioactive contamination, Britain's Health Protection Agency said.

The agency said 106 staff at Barnet General Hospital and University College Hospital had been assessed for possible exposure, and 49 would have their urine tested.

The mysterious death has clouded Anglo-Russian relations. Prime Minister Tony Blair said Tuesday that police were determined to find out who was responsible for Litvinenko's death.

"The police investigation will proceed, and I think people should know that there is no diplomatic or political barrier in the way of that investigation," Blair said in Copenhagen, Denmark. "It is obviously a very, very serious matter indeed. We are determined to find out what happened and who is responsible."

Media reports in Britain and Russia on Wednesday said that Litvinenko had been engaged in smuggling nuclear substances out of Russia.

The Independent newspaper reported that Litvinenko told Scaramella on the day he fell ill that he had organized the smuggling of nuclear material for his former employers at Russia's Federal Security Service, or FSB. The newspaper reported that Litvinenko said he had smuggled radioactive material to Zurich in 2000.

But Scaramella told the AP that he had been misquoted by the newspaper.

"He (Litvinenko) wanted to see me because he knew about smuggling of nuclear material, but as far as I know he was never involved in nuclear smuggling," he said.

Scaramella said he had been cleared of any involvement in the 43-year-old former spy's death.

"Let me take the opportunity to say that I'm not under investigation by any British authority," he said. "I am cooperating with them (the police)." Police declined to say whom they had spoken to.

Scaramella said he showed Litvinenko e-mails from a confidential source identifying the possible killers of Russian investigative journalist Anna Politkovskaya and listing other potential targets for assassination — including himself and Litvinenko.

Following Litvinenko's death, more than 1,100 people called a health hot line over concerns they might be at risk from polonium poisoning, which is deadly in tiny amounts if ingested or inhaled. Sixty-eight have been referred to health authorities, the Health Protection Agency said — including the 49 hospital staff.

Eight have been referred to a special clinic as a precaution. The tests should take about a week.

Traces of radiation have been found at six sites visited by Litvinenko.

A coroner will perform an autopsy on Litvinenko on Friday, "subject to appropriate precautions," said the local authority responsible, Camden Council. Doctors had sought expert advice on whether Litvinenko's radioactive body posed a threat to those performing the post-mortem.

A coroner's inquest will be opened Thursday and then adjourned until the police investigation is complete, the council said.

FOX News' Greg Palkot and The Associated Press contributed to this report.