Russian businessman Dmitry Kovtun, a key figure in the poisoning investigation of ex-security agent Alexander Litvinenko, is in a coma, a Russian news agency said today, but a lawyer close to the case denied the report.

Russia has opened a criminal case in the poisoning death of ex-spy Alexander Litvinenko and for the attempted killing of associate Dmitry Kovtun, the Prosecutor General’s office said today.

Ex-Russian spy Alexander Litvinenko, who died last month after being poisoned, was scheduled to be buried in London today, his friends said.

Russian investigators said they have begun questioning in the radiation poisoning death of former Russian agent Alexander Litvinenko, a case that has left radiation traces from a London soccer stadium to the British Embassy in Moscow.

Experts have found minor traces of radiation at the British Embassy in Moscow but they presented no health risk to the public, an embassy spokesman said today.