LONDON - A coroner says a British spy whose naked body was found inside a locked sports bag was likely killed in a criminal act, but acknowledged the riddle of how he met his mysterious death may never be solved.

Coroner Fiona Wilcox said Wednesday it was unlikely that the demise of codebreaker Gareth Williams, 31, would "ever be satisfactorily explained," despite a 21-month police inquiry, and seven days of expert evidence to an inquest hearing.

Williams worked for Britain's secret eavesdropping service GCHQ but was attached to the MI6 overseas spy agency when his remains were found in August 2010 at his London apartment, in the bag and inside a bathtub.

Wilcox said the spy was likely killed either by suffocation or poisoning in a "criminally meditated act."