LONDON — Even after a coroner’s verdict, it remains a mystery: A naked spy found dead in a locked bag, lurid details of a kinky sex life and allegations that someone in Britain’s spy agencies may have been involved in his death.

A British coroner ruled Wednesday that another person was likely involved in Gareth Williams’ death — a finding that puts more pressure on police to uncover the cyberwarfare expert’s killer and continue to investigate possibilities that include whether he could have died in a sex game gone awry or in a more sinister scenario that involved his counterterrorism work.

In Britain, coroners are asked to investigate unexplained deaths, and their findings can often carry weight as police investigations proceed.

Although Coroner Fiona Wilcox said it was unlikely that the death of Williams, 31, will ever be “satisfactorily explained,” she said the spy was likely killed either by suffocation or poisoning in a “criminally meditated act.” She also said it was possible that someone from one of Britain’s spy agencies was involved.

Williams, described as an introverted math genius, worked for Britain’s secret eavesdropping service GCHQ. But he was attached to the MI6 foreign spy agency when his remains were found in the bathtub at his London apartment on Aug. 16, 2010, just a few days after returning from a trip to the United States.

Forensic experts found some $32,000 worth of luxury women’s clothing, shoes and wigs in his apartment. Police also discovered that he had visited bondage and sadomasochism websites, including some related to claustrophilia — a desire for confinement in enclosed spaces.

William’s landlord testified during the coroner’s hearing that she once found him handcuffed to his bed. She said he had appeared embarrassed after asking for help.

Still, Wilcox said there was no immediate evidence of a sexual encounter gone wrong, of suicidal intent, or that Williams’ death was linked to a supposed interest in bondage.

She said, however, that tales about his sex life could have been fueled in an attempt to “manipulate the evidence.”

In the past, spy recruits were often cautioned that their sex lives could make them vulnerable to blackmail.

The case has frustrated Scotland Yard detectives who have been investigating the case for 21 months now and say that the secrecy surrounding Williams’ job has thwarted their efforts.

“Obviously a lot of information has come out through the course of this inquest which we have not been party to,” lead detective Jackie Sebire said.

But Wilcox also criticized the police detectives. Time and resources were wasted, she said, when forensic teams investigating a DNA sample taken from Williams’s hand later turned out to belong to one of the forensic scientists. She also questioned the handling of William’s iPhone, which contained deleted images of him naked in a pair of boots.