German police said Saturday that they had found traces of radiation at two sites in and near Hamburg linked to a contact of poisoned former Russian spy Alexander Litvinenko.

Police said they found traces of alpha radiation at the Hamburg apartment of the ex-wife of Dmitry Kovtun, who met Litvinenko in London on Nov. 1, the day the former spy is believed to have fallen ill.

They also said an initial scan had shown contamination at the home in Haselau, west of the port city, of his ex-wife's mother.

Police say they began their checks following media reports that Kovtun had flown to London from Hamburg.

Specialists found no trace of polonium-210, the rare radioactive substance that killed Litvinenko, at the apartment of Kovtun himself in the Hamburg district of Ottensen.

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However, police said in a statement Saturday they found "contamination that makes a fine examination necessary" at two locations in an apartment in the same building used by Kovtun's ex-wife.

They said during the night they had found indications that there had been a source of radiation in the apartment, but added that they had not found the source.

Police later sealed off a property in Haselau, outside Hamburg, for further tests after finding traces of contamination there.

The traces were found in the bathroom and living room of the Hamburg apartment, and on a bed and a chair at the property in Haselau. Further tests were to determine whether the contamination was linked to polonium-210.

Kovtun's ex-wife and her mother were questioned by police. Authorities did not identify the 31-year-old ex-wife.

Kovtun, one of two Russians who met Litvinenko at London's Millennium Hotel, is reportedly being treated in Moscow, also for radiation poisoning.

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Police spokeswoman Ulrike Sweden said early Saturday that it was unclear whether Kovtun had returned to Hamburg after meeting Litvinenko.

She said it was possible that either a person or an object could have been the source of radiation in the Hamburg apartment.

While German authorities were in contact with British police, the search was "purely protective" and not part of any investigation against Kovtun, Sweden said.

Police have said the traces found so far represent no health risk to local residents. However, they said that about 30 people who live in the Hamburg apartment building would have to vacate it while tests continue.