Ex-Russian spy Alexander Litvinenko, who died last month after being poisoned with a rare radioactive element, was to be buried Thursday in London - as police continued an exhaustive international hunt for his killer. Around 30 family members and friends have traveled to Britain from Russia, Italy and the United States to attend the ceremony in north London, according to a family friend who spoke on condition of anonymity because he was not authorized to release details about the service. British police on Wednesday confirmed the former agent's poisoning was now being treated as murder - rather than as a suspicious death. Officers who have traveled to Moscow to investigate the case have interviewed some of the five men they hoped to question in connection with the killing, police said. The British investigators were expected to meet Thursday with one of the key figures in the case, Andrei Lugovoi, his lawyer Andrei Romashov told The Associated Press in Moscow.