The New York Post reports that the radioactive toxin used to kill Alexander Litvinenko has been traced to Russia (from the front page; the paper also has an editorial based on the story entitled "Paying Putin's Price" and the Times of London also has elaborate update coverage). The editorial states:

Putin, of course, says that any suggestion he's involved in these attacks - including the death of Litvinenko, one of his harshest critics - is 'absolute nonsense' and a "political provocation. Problem is, no one believes him - and with good reason. Why would Putin risk international condemnation by liquidating Litvinenko in a way that ensures the fingers of suspicion point to him? Probably because that's the way the thugs at the Kremlin have always disposed of their pesky domestic critics. And because, given the need for Putin's cooperation on major strategic issues, the international community has shown little interest in holding him accountable.

The Kremlin is trapped now, having failed to previously report that any radioactive material had gone missing (The New York Times reported: "Last week, Russia’s top nuclear official said it exports 8 grams of polonium 210 a month, or 96 grams a year, to the United States. That is 3.4 ounces, which seems like a trifle but in theory is enough for thousands of lethal doses. He also said Russia had made no exports to Britain in the past five years. 'Allegations that someone stole it during production are absolutely unfounded,' Sergei Kiriyenko, director of the Russian Federal Atomic Energy Agency, said on Tuesday. 'The controls are very tough.'"). The brilliant Scotland Yard is closing in. A furious Times of London editorial declares that Britain is "no place to settle scores" and states: "Whether we will ever get to the bottom of who killed Mr Litvinenko remains unclear. But one thing is all too obvious: another country’s battles are being waged on British soil and are putting British lives at risk."

The Post reports:

High-tech detective work by British scientists has traced the radioactive poison that killed ex-spy Alexander Litvinenko in London back to a nuclear power plant in Russia - further fueling the belief that Russian President Vladimir Putin was behind the murder, it was reported yesterday.

The "fingerprint" of the fatal isotope was revealed by officials of the Atomic Weapons Establishment from the various London sites and British Airways jets that have been contaminated with traces of polonium-210, London's Evening Standard newspaper said.

Placing the origin of the poison in Russia only adds more credence to the claims that Putin wiped out Litvinenko - one of his harshest critics - as the spy himself charged on his deathbed.

The power plant was not named by the agency, which provides material for Britain's nuclear arsenal.

The report came as British authorities disclosed that an Italian security expert who met Litvinenko on the day the ex-spy fell fatally ill has tested positive for the poison.

But there were conflicting reports on how much of the rare isotope contaminated Mario Scaramella.

Early yesterday British authorities described it as a "significant quantity."

As a result, Britain's Anti-Terror Group began investigating whether Scaramella was intended to be the second victim in a bizarre murder plot, The Times of London reported today.

Radiological experts concluded the amount found in Scaramella was more than what he could have gotten from casual contact with Litvinenko at the table they shared in a London sushi restaurant on Nov. 1.

"My son has been poisoned" was all that his father, Amedeo Scaramella, said when contacted by telephone yesterday.

But late yesterday Mario Scaramella was described as "well and showing no signs of radiation poisoning." He is under protection at University College Hospital in London and undergoing extensive medical tests.

Last week, Scaramella said that during their lunch he showed Litvinenko evidence that he and Litvinenko were targets of the same killers who murdered the ex-spy's friend, investigative journalist Anna Politkovskaya, in October.

Hours after the lunch, Litvinenko, 43, showed the first symptoms of the poisoning that killed him on Nov. 23. Before he died, he accused Putin of ordering his poisoning.

In other developments in the international whodunit case:

* Litvinenko's wife also tested positive for the poison, polonium-210, but showed no signs of illness.

Marina Litvinenko was "very slightly contaminated," said Alex Goldfarb, a friend of her husband's.

"It is a fraction of the lethal dose that Mr. Litvinenko himself had," British Home Secretary John Reid said.

* A hotel in Sussex, southeastern England, was evacuated briefly as police and health workers carried out tests for polonium-210. The hotel had been visited by Scaramella after he met with Litvinenko.

"Police said they found nothing of any concern," Graeme Bateman, the hotel's managing director, said after it was reopened.

* A British government source said Italy may follow Britain's lead and check levels of radiation on their aircraft, apparently because of Scaramella.

A spokesman for Easyjet said Scaramella had flown with it from his hometown of Naples to London on Oct. 31 and back again on Nov. 3.

* Authorities were also testing Dublin's James Connolly Memorial Hospital, which treated former Russian Prime Minister Yegor Gaidar.

Aides of Gaidar suspect he was also poisoned while attending a conference in Ireland last week.

* Three pathologists wearing protective suits to guard against radiation carried out a post-mortem on Litvinenko at the Royal London Hospital. No details of the autopsy were expected for several days.

* Litvinenko's family was told he will have to be buried in a sealed coffin to prevent further contamination, the BBC reported. If relatives wanted the remains to be cremated they will have to wait 22 years, the network said.

The disclosure about Scaramella's polonium contamination raised new questions such as how he could have been poisoned.

In a deathbed interview, Litvinenko said Scaramella "ate nothing" during their Nov. 1 lunch. Scaramella only drank a liter of water.

Doctors now say Scaramella has a "considerably lower" level of polonium than Litvinenko. But his body apparently contains more of it than he could have gotten from shaking hands or sharing the same air at the restaurant.

Another mystery is why Scaramella insisted earlier this week that he had been told by doctors he wasn't at any risk.

"I am fine. I am not contaminated and have not contaminated anybody else," he told a reporter on Wednesday.

Yesterday doctors who examined him said it would take weeks before they know if he faces a long-term danger such as cancer. The body does not naturally eliminate polonium-210.

Italian Senator Paolo Guzzanti, who spoke to Scaramella's lawyer yesterday, said Scaramella "is very depressed."

But the latest development appeared to put to rest conspiracy theories claiming he was involved in the poisoning of Litvinenko.

Scaramella describes himself as a security consultant. Since his name surfaced in the case last month, he's also been described as an environmental law professor, a shadowy information-peddler and a respected investigator with ties to Italian and Russian intelligence.

Italian media have reported that Scaramella is being investigated for arms trafficking, but his lawyer says he has not been notified of any investigation.

He won high praise from Guzzanti for his contributions to a parliamentary investigation, headed by Guzzanti, that exposed Russian agents in Italy.

During the Guzzanti probe, Scaramella met Litvinenko, who obtained asylum in Britain in 2000 because, he said, he refused to carry out murderous orders of the FSB, the successor to the KGB.

During Putin's tenure in the Kremlin, the FSB has been expanded from a domestic security agency and is authorized to carry out operations beyond Russian borders.

From his hospital bed, Litvinenko recalled that he unexpectedly heard from Scaramella again in October when the Italian e-mailed him to say he had key information about the murder of Politkovskaya.

"Mario said he wanted to sit down to talk to me," Litvinenko told The Sunday Times of London. They met at the sushi bar in London, where a "very nervous" Scaramella gave him a four-page e-mail.

After the lunch, Scaramella "disappeared," but Litvinenko said he was not accusing him of wrongdoing.

Russian officials have steadfastly denied any involvement in Litvinenko's death.

Foreign Minister Sergei Lavrov said yesterday that Russia hasn't even received a formal inquiry from Britain about the case.

"The ball is now in Britain's court," he said.

Putin supporters have hinted at other possible suspects, including Litvinenko's mentor, exiled billionaire Boris Berezovsky.

Another theory being pursued by British investigators is that Litvinenko was killed after a falling out with Russian businessmen.