Traces of the rare radioactive substance polonium-210 were found at a German apartment visited by a contact of fatally poisoned ex-spy Alexander Litvinenko ? before the two men met in London, authorities said recently.

The polonium traces were found on a couch where Russian businessman Dmitry Kovtun is believed to have slept at his ex-wife?s Hamburg apartment the night before he headed to London for a meeting with Litvinenko last month, German investigators said.Tests on traces of radiation at the apartment ?clearly show that it is polonium-210,? Gerald Kirchner of the Federal Radiation Protection agency said at a news conference.

Investigators said Kovtun flew to Hamburg from Moscow with Aeroflot on October 28 and departed for London on November 1. That is the day when Kovtun and at least one other Russian met with Litvinenko at London?s Millennium Hotel ? and when Litvinenko is believed to have fallen ill.Traces of radiation also were found in the passenger seat of a car that picked Kovtun up from the Hamburg airport, on a document Kovtun brought to Hamburg immigration authorities and at the home of Kovtun?s ex-mother-in-law outside Hamburg ? all from before the November 1 meeting. German prosecutors did not say whether they suspect Kovtun might have been involved in Litvinenko?s death. But they said they were investigating him on suspicion he may have improperly handled radioactive material.?At this stage of the investigation, we have sufficient initial cause to believe that he brought the polonium traces to Hamburg outside his body, or that these traces are the result of contact with polonium-210,? prosecutor Martin Koehnke said.