A spy whose naked, decomposing body was found inside a padlocked gym bag at his apartment likely died in an accident with no one else involved, British police said Wednesday _ a tentative conclusion that is unlikely to calm conspiracy theories around the bizarre case.

Metropolitan Police Deputy Assistant Commissioner Martin Hewitt said the death of Gareth Williams, whose remains were found inside a bag in his bathtub in August 2010, was "most probably" an accident, but that the facts could not be established beyond a reasonable doubt.

Hewitt said that a police review had found little evidence of foul play in a death that has spawned a host of theories, from assassination to sexual adventure gone awry.

Williams worked for Britain's GCHQ eavesdropping service and was attached to the overseas espionage agency MI6 when he died.

The police verdict disagrees with a coroner's inquest, which concluded that Williams had probably been killed by another person in a "criminally meditated act."

Hewitt said the police position "is that, on balance, it is a more probable conclusion that there was no other person present when Gareth died."

??"But the reality is that for both hypotheses, there exist evidential contradictions and gaps in our understanding."

Some have raised the possibility that Williams locked himself in the bag as part of a sex game gone wrong. Investigators found that he had visited bondage and sadomasochism websites, including some related to claustrophilia _ a desire for confinement in enclosed spaces.

However, none of Williams' DNA was found on the lock on the bag and his palm prints were not found on the rim of the bath.

But Hewitt said there was no evidence that the flat had been cleaned to remove forensic traces and nothing to suggest a struggle or a break-in.

"I believe that what we are dealing with is a tragic unexplained death," he said.

Williams' relatives said in a statement that they were disappointed that the facts were still not clear, but still believed it was likely he had been killed.

"We consider that on the basis of the facts known at present the coroner's verdict accurately reflects the circumstances of Gareth's death," the statement said.