Russian investigators plan to visit London to conduct inquiries into the killing of Alexander Litvinenko, Moscow authorities said, as forensic teams combed two houses and an aircraft in Germany and a London hotel thought to lie at the center of the ex-Soviet spy's poisoning. Litvinenko's widow, in her first public comments since his death, said she did not want to help Russian authorities with their investigation. "I can't believe that they will tell the truth," Marina Litvinenko was quoted as saying by The Mail on Sunday newspaper. "I can't believe if they ask about evidence they will use it in he proper way." Police in Germany said on Saturday that traces of radiation had been found at two Hamburg-area homes linked to a contact of Litvinenko, who died last month after being contaminated with the radioactive element polonium-210. Officials also tested a plane from airline Germanwings that was used by Russian businessman Dmitry Kovtun, who met Litvinenko in London on the day Litvinenko became ill. Germanwings said no traces of polonium-210 were found on the Airbus A-319 Kovtun took from Hamburg to London on Nov. 1. German police did, however, find traces of radiation at Kovtun's ex-wife's Hamburg apartment, and an initial scan also yielded signs of contamination at his former mother-in-law's home in Haselau, west of the port city. Kovtun reportedly is being treated in Moscow, also for radiation poisoning, although there have been conflicting reports about his condition. At London's Millennium Hotel in Mayfair _ where Litvinenko drank tea in the Pine Bar on Nov. 1 with Kovtun and a group of fellow Russians, and where he appears to have been poisoned _ officers were testing a cup and a dishwasher for traces of polonium, Britain's Daily Telegraph said. Officials said they could not immediately comment on the report. Litvinenko, 43, died in London on Nov. 23 after blaming President Vladimir Putin for his poisoning in a deathbed message _ an accusation the Kremlin has vehemently denied. In Moscow, the Prosecutor General's office said Saturday that officials would travel to Britain as part of a Russian inquiry into the killing, but did not confirm if suspects would be questioned. A spokeswoman for Moscow's Prosecutor General's office said it there were plans to send Russian investigators to London but no concrete date for their departure. She said she was not authorized to give her name to media. British police said they had no details of the planned visit by Russian investigators, but government authorities said they would consider any request from Moscow for access to exiles granted political asylum. Andrei Nekrasov, a friend of Litvinenko, said there was concern among emigres in the British capital that the Kremlin would use the inquiries as a "pretext to harass exiles in London." Litvinenko and his emigre allies have blamed Russian President Vladimir Putin for the poisoning _ a charge the Kremlin strongly denies. Marina Litvinenko told The Mail on Sunday she did not believe Putin was personally responsible for the death of her husband, who acquired British citizenship this year. "Obviously it was not Putin himself, of course not," she said. "But what Putin does around him in Russia makes it possible to kill a British person on British soil. I believe that it could have been the Russian authorities." Nekrasov said former Russian security officer Mikhail Trepashkin, who is serving a four-year prison sentence after being convicted of divulging state secrets, had said a Kremlin agent previously ordered to monitor Litvinenko was among those appointed to investigate the killing. The Sunday Telegraph newspaper reported that Trepashkin had named a serving colonel in the FSB as a figure "of key importance" in the poison plot. The newspaper said it knew the man's identity, but was not publishing it for legal reasons. Andrei Lugovoi, also an ex-Soviet agent, Kovtun and Vyacheslav Sokolenko, the head of a private Russian security firm, joined the Nov. 1 meeting with Litvinenko in the Millennium Hotel's intimate, blond oak-paneled bar. Lugovoi has denied the men were involved in the ex-spy's death. British detectives who traveled to Moscow last week as part of their investigation still have not spoken to Lugovoi, for reasons that remain unclear. Lugovoi said he was not questioned Saturday and probably would not be before Monday, Russian news agencies reported. Litvinenko later met with Mario Scaramella, an Italian security expert, at a Piccadilly sushi bar. By evening, the former agent was ill with stomach pains and nausea. He died within weeks from radiation poisoning that caused his hair to fall out and organs to fail. All seven staff working at the bar on Nov. 1 showed evidence of exposure to polonium-210, Britain's Health Protection Agency said. Scaramella was hospitalized last week in London and later released after he showed low levels of polonium-210, but no symptoms. Dr. Michael Clark of the Health Protection Agency said it was likely Litvinenko's poisoning occurred at the hotel bar. He said food, drinks and cigarettes all could have been used to deliver the poison. Around 200 other people who visited the hotel bar on Nov. 1 were being contacted and offered tests, British health officials said.