British police on Tuesday completed more than two weeks of work in Russia investigating the killing of Alexander Litvinenko, a former Russian security agent who died of poisoning in London, the Prosecutor-General's office said.
Litvinenko's death Nov. 23 from poisoning by the radioactive isotope polonium-210 strained Russian-British relations and set off speculation that he was killed by agents working for the Kremlin or by people trying to discredit President Vladimir Putin.
The British investigators, who arrived in Moscow on Dec. 4, "were shown complete and all-around assistance," the Prosecutor-General's office said in a statement.
The statement said the investigators on Tuesday were given an array of material, including transcripts of witness questioning, reports AP.
The British investigators were not allowed to question witnesses themselves, but observed as Russian investigators conducted questioning.
It was not immediately clear when the investigators would return to Britain. The British Embassy had no immediate comment on the prosecutor's office statement.