30,000 BA passengers alerted after radiation found on two airliners

Radioactive contamination has been found on two British Airways passenger jets at Heathrow by scientists involved in the investigation into the poisoning of the former Russian agent Alexander Litvinenko.

Traces of a nuclear material believed to be polonium-210 were found on BA aircraft used on the London-to-Moscow route. A third aircraft was grounded in Moscow last night while tests were carried out to see if it is also contaminated.

It is understood that Scotland Yard ordered tests to be performed on the planes as part of its investigation into the movements of individuals who were in London around the time Mr Litvinenko fell ill on 1 November.

Up to 800 people were on board the planes during the four flights under investigation between 25 October and 3 November, and a further 30,000 passengers and 3,000 staff are estimated to have travelled on the 221 flights the aircraft made before being grounded.

BA chief executive Willie Walsh said concerned passengers should contact NHS Direct or their doctor. He said: "At this stage we want to reassure our customers in relation to this. The advice that we have is that the risk to public health is actually very, very low."

The flights being investigated are BA875 from Moscow to Heathrow on 25 October, BA872 from Heathrow to Moscow on 28 October, BA873 from Moscow to Heathrow on 31 October and BA874 from Heathrow to Moscow on 3 November.

In a statement, the airline said: "The initial results of the forensic tests have shown very low traces of a radioactive substance on board two of the three aircraft. British Airways has been advised that this investigation is confined solely to these three Boeing 767 aircraft, which will remain out of service until further notice."

It is the latest crisis beyond British Airway's control to hit the airline, less than four months after delays and flight cancellations as a result of hand luggage restrictions imposed in the wake of anti-terror raids and arrests in Walthamstow and High Wycombe.

The findings will refocus attention on a meeting on 1 November between Mr Litvinenko and two Russian businessmen at the Millennium Hotel in Mayfair. One of the men, Andrei Lugovoy, a former KGB bodyguard, had travelled from Moscow to watch a football match between CSKA Moscow and Arsenal. Mr Lugovoy has denied any involvement in Mr Litvinenko's death: in a press conference in Moscow with his business associate Dimitri Kovtun the pair stressed that alcohol was the strongest "poison" they had offered Mr Litvinenko.

The development came as the Italian academic who also met Mr Litvinenko on the day he fell ill said tests at a London hospital had shown he was not contaminated. Mario Scaramello was being interviewed by detectives last night after he voluntarily returned from Italy on Monday. He is being questioned as a potential witness.

Detectives from the Yard's anti-terrorist branch are continuing to try to piece together the movements of Mr Litvinenko on 1 November, when he met Mr Scaramella at a branch of the Itsu restaurant chain, the first of several meetings held by the former Russian agent that day.

Mr Scaramella, who had known Mr Litvinenko for five years and claimed the former Russian intelligence officer told him he was involved in smuggling nuclear material, said: "I am fine. I am not contaminated and have not contaminated anybody else."

In a further twist to the mystery, a former Russian prime minister, who was once guarded by one of those who met Mr Litvinenko on 1 November, was being treated in a Moscow hospital last night after falling ill while visiting Dublin. Yegor Gaidar, 50, who is a veteran of the liberal opposition to Russian president Vladimir Putin, collapsed while on a tour to publicise a new book, Death of the Empire, about the fall of Communism.

He was flown back to Moscow yesterday where friends drew a parallel with the deaths of Mr Litvinenko and the dissident journalist Anna Politkovskaya, who was murdered in Moscow last month. His daughter, Maria, said: "Doctors are trying to come up with a diagnosis but they can't find one. His condition is satisfactory and he is speaking but he looks very bad ­ he looks pale and thin."

She added that doctors were trying to diagnose his "rather strange symptoms", including a nose bleed and loss of consciousness. A friend, Anatoly Chubais, said his condition appeared to be life-threatening.

"He was in the balance between life and death. Could this simply be some sort of natural illness? According to what the doctorssay ­ no."

The Health Protection Agency said 49 members of staff at the two London hospitals where Mr Litvinenko was treated had been asked to provide urine samples to test for exposure as a "precaution".

An inquest will open today into the death of Mr Litvinenko last Thursday, some three weeks after he swallowed a lethal quantity of polonium-210.