BERLIN, December 9 (RIA Novosti) - Police in the German city of Hamburg on Saturday reported finding traces of radiation in places visited by a key witness in the murder case of former Russian intelligence agent Alexander Litvinenko.

Massive radiation checks are being carried out in Britain, Russia, and Germany as part of an international investigation into the murder of Litvinenko, who died in London November 23 of poisoning caused by radioactive substance polonium 210.

No radiation has been detected in Russian spy-turned-businessman Dmitry Kovtun's Hamburg apartment, but his ex-wife's flat in the suburb of Pinneberg has proved contaminated.

Kovtun, who met with Litvinenko in London shortly before the exiled spy was taken to hospital and diagnosed with poisoning, is now reported to have been hospitalized with similar symptoms. His lawyer, however, has dismissed the reports about Kovtun's illness.