Detectives are now treating the death of ex-Russian spy Alexander Litvinenko as "suspicious", Home Secretary John Reid has said.
Mr Reid told Radio Clyde: "As at this stage, they're saying to me that they now regard the death as suspicious.
"That wasn't the case yesterday, for instance."
Until now police have said they were treating it as an unexplained death, although they previously said they suspected deliberate poisoning.
A Scotland Yard spokesman was not immediately able to comment on Mr Reid's words.
Mr Litvinenko, 43, died in hospital on Thursday night after receiving a large dose of the radioactive substance Polonium-210.
A vocal critic of Vladimir Putin, he claimed in a statement made public after his death that the Russian president had had him poisoned.
Health chiefs have called for customers at a restaurant and a hotel that he visited on the day he was taken ill to come forward to try to rule out concerns that anyone else may have received radiation poisoning.
Scientists at the Health Protection Agency are due to begin receiving urine samples from some of them to test.
