MOSCOW, Dec 15: British and Russian investigators questioned a witness on Friday in the radiation death of fugitive Russian agent Alexander Litvinenko, as questions arose over the condition of two other key figures in the inquiry.

Interfax news agency quoted sources close to the inquiry as saying that Scotland Yard detectives and officials from the Russian prosecutor general's office interviewed Vyacheslav Sokolenko for more than four hours. Where the meeting took place was not clear.

Sokolenko, a former KGB officer who now works for a private bodyguard firm based in Moscow, was one of the last people to see Litvinenko on November 1 before the ex-security services agent fell sick. Litvinenko died on November 23 from radioactive polonium 210 poisoning.

Meanwhile, questions grew over the health of two other vital witnesses, Dmitry Kovtun and Andrei Lugovoi, who had met Litvinenko for drinks at the Millennium Hotel in London just before Sokolenko arrived.

Lugovoi has been reportedly undergoing tests for radiation poisoning in Moscow. He had been quoted earlier as saying that he expected to receive a doctor's final report by the end of this week.

Lugovoi said that “the medical investigation will continue next week,” Interfax reported.

Lugovoi, who has already met once with British and Russian investigators, said he did not “exclude another interview,” Interfax reported. The news agency quoted an unidentified source as saying that Kovtun, who is said to be undergoing treatment for radiation poisoning, could be questioned on Monday or Tuesday — also for a second time.—AFP