A key witness in the poisoning death of former Russian security agent Alexander Litvinenko was questioned Monday by British investigators in a Moscow hospital, where he was undergoing radiation checks, Russian news reports said.

German authorities, meanwhile, have found traces of polonium-210, the rare radioactive substance that killed Litvinenko, in locations visited by his Russian contact before their meeting.

Andrei Lugovoi, a security agent-turned businessman who met with Litvinenko in a London hotel on Nov. 1, the day he was poisoned, was supposed to testify after a team of Scotland Yard officers arrived in Moscow on Dec. 4. The British investigators had tried all last week to interview him without success, British law enforcement officials have said.

Lugovoi finally spoke to investigators at a Moscow clinic, where he was undergoing checks for radioactive contamination. He later told the ITAR-Tass and Interfax news agencies that the questioning lasted three hours.

"I gave testimony exclusively as a witness. I was officially informed of that before the interrogation," ITAR-Tass quoted him as saying. "They made no charges against me."

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Lugovoi said the results of his medical tests would be known later this week, but added that he was "unlikely" to make them public.

Neither the Russian Prosecutor General's Office, which is managing the British investigators' program in Moscow, nor the British Embassy would reveal any details of the investigation.

British Ambassador Anthony Brenton met Monday with Russia's Prosecutor General Yuri Chaika to discuss the British inquiry into Litvinenko's death. "We are getting the cooperation that we need," Brenton told AP Television News later Monday.

Another central figure in the case, Russian businessman Dmitry Kovtun, a business associate of Lugovoi who accompanied him during the Nov. 1 meeting with Litvinenko, is believed to be staying in the same hospital. Russian Prosecutor General's office said Kovtun had been diagnosed with radioactive poisoning.

Lugovoi told the RIA Novosti news agency Monday that Kovtun was in stable condition and "feeling normal."

Russian and British investigators interviewed Kovtun last week before German investigators found traces of polonium-210 in Hamburg, the city where he spent four days immediately before he met with Litvinenko in London on Nov. 1.

Traces of polonium-210 have now been confirmed in a Hamburg apartment of Kovtun's ex-wife, where he spent two nights, and the car that picked him up from the Hamburg airport when he arrived from Moscow.

On Monday, police said that the ex-wife, her partner and two small children were taken to a Hamburg hospital for tests to check whether they absorbed any radiation.

The family showed no signs of external contamination, prompting tests to determine whether they ingested a radioactive substance. They might have been contaminated, for instance, by eating with the same cutlery or drinking from the same glass.

German prosecutors are investigating Kovtun on suspicion that he may have illegally handled radioactive material. They have left open whether the radioactive trail meant he might have been involved in Litvinenko's poisoning, saying that he may have been a victim or could have been involved in procuring the polonium.

Lugovoi, Kovtun and a third associate who was in London with them on the weekend of Nov. 1, Vyacheslav Sokolenko, have denied involvement in Litvinenko's death.

Litvinenko died in London on Nov. 23, blaming the Kremlin for poisoning him — accusations Russian officials vehemently deny.

During a meeting with Brenton on Monday, Russian Prosecutor General Yuri Chaika "noted the interest of the Russian Federation in the objective and multifaceted investigation of the facts of the death of Alexander Litvinenko," Chaika's office said in a statement.

Russian prosecutors have opened their own probe into the murder of Litvinenko and attempted murder of Kovtun, and Chaika's office said Saturday it was going to send investigators to London as part of the inquiry.

The move to open a criminal investigation in Russia would allow suspects to be prosecuted in Russia. Officials previously have said Russia would not extradite any suspects in Litvinenko's killing.

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