An Italian academic who met former Russian spy Alexander Litvinenko the day he became ill from radiation poisoning is under police protection in London and undergoing medical tests.
Mario Scaramella, who has advised an Italian parliamentary commission on Soviet-era espionage, is being checked to find out if he too has been contaminated. Litvinenko died on Thursday.
Italian academic Mario Scaramella
Significant amounts of radioactive Polonium 210 were found in the body of Mr Litvinenko, a former agent who became a fierce Kremlin critic and accused Russian President Vladimir Putin of ordering his death.
Moscow denies involvement.
Traces of Polonium 210 were also found at the London sushi restaurant where Mr Litvinenko met Mr Scaramella on November 1st.
Mr Scaramella has said he showed Mr Litvinenko emails from a mutual source warning their lives may be danger from St. Petersburg-based criminals.
The emails said the same criminals, possibly acting on behalf of Moscow, had killed prominent journalist Anna Politkovskaya last month.
Mr Litvinenko had been investigating Ms Politkovskaya's death. He had also published a book accusing Russian security services of carrying out Moscow apartment bombings in 1999 that were blamed on Chechen rebels and used by
Mr Putin as justification for war against the separatists.