Police investigating the poisoning of former Russian spy Alexander Litvinenko have extended their search to a five-star London hotel.
Scotland Yard confirmed that officers were examining the Sheraton Park Lane Hotel as well as an office building in the West End.
The fresh searches came as as it emerged that eight people were being tested for possible contamination following the death last week of the ex-KGB man, an outspoken critic of Russian president Vladimir Putin.
Although a post-mortem examination is yet to take place on Mr Litvinenko's body, tests have already shown "significant" quantities of the radioactive substance polonium 210 in his urine.
Traces of the substance have been found at a series of other London addresses including the offices of exiled Russian billionaire Boris Berezovsky.
Scotland Yard said police examinations were taking place at 58 Grosvenor Street in Mayfair and the Sheraton Park Lane Hotel on Piccadilly. Police have already found traces of the substance at another site in Grosvenor Street, the offices of an international security company.
A Scotland Yard spokeswoman said: "We can confirm that police examinations are taking place at 58 Grosvenor Street and the Sheraton Park Lane Hotel in connection with the Alexander Litvinenko death."
A Health Protection Agency (HPA) spokeswoman confirmed that experts had already conducted tests in "key public areas" of the hotel and found no risk of radiation poisoning. Further tests are expected in any areas identified by the police investigation.
She added that the agency had yet to carry out tests at 58 Grosvenor Street but would do so as soon as the police investigation made that possible.
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Earlier the HPA revealed that more than 1,100 people had called a national helpline concerned that they could have been exposed to the deadly element, of whom eight have been referred to a specialist assessment clinic. Home Secretary John Reid said that the eight were being tested for their own reassurance, describing the tests as "very precautionary".
