Further tests will be carried out on the body of a murdered British spy to establish how he died after a post-mortem examination proved inconclusive.
Gareth Williams' decomposing remains were found by police stuffed inside a holdall in the bath of his London home on Monday. His body may have lain undiscovered for up to a fortnight.
Officers broke down the door after attempts by the Foreign Office to locate him via his former landlady failed.
On Wednesday night a Home Office pathologist failed to find a cause of death following a post-mortem examination of Mr Williams' body. Further tests, including toxicological analysis of his blood for evidence of drugs and alcohol, will now take place. Detectives were unable to say when these tests would happen.
Investigators from the Met's homicide and serious crime command labelled the death as "suspicious and unexplained". Sources said there was no evidence Mr Williams was stabbed, contradicting earlier reports.
Forensic officers spent two days scouring Mr Williams' top-floor flat in Alderney Street, Pimlico, for clues as to what happened in his final hours.
Originally from Holyhead, North Wales, he was on secondment to MI6 from his job as a communications officer at the GCHQ "listening post" in Cheltenham, Gloucestershire.
Sources close to the inquiry said it was not clear how he died and played down speculation that the murder was linked to his secretive line of work.
One source said: "The suggestion there is terrorism or national security links to this case is pretty low down the list of probabilities."