MI6 did not hand over to police nine computer memory sticks belonging to spy Gareth Williams during the investigation into his death, an inquest has heard.
Officers discovered that MI6 withheld a North Face bag similar to the one Williams was found and the memory sticks.
The intelligence service had examined electronic media belonging to the code-breaker but failed to pass on a full inventory of his possessions at work.
The existence of the memory sticks was only revealed on the final day evidence at the inquest.
The body of Williams, 31, was found locked in a North Face holdhall at his Pimlico flat in London in August 2010.
DCI Jackie Sebire, the police officer leading the investigation, told Westminster's coroner's court that she "would have expected to have been told" about the belongings in 2010.
"What I knew was that Gareth's email accounts had been checked, but I did not know that other media had been checked," said Sebire.
She added that she was not surprised that Williams had memory sticks at his office given his line of work.
It is not clear how relevant they could be to the investigation.
DC Colin Hall, of the counter-terror SO15 branch, was questioned about his search of Williams's MI6 office.
Hall told the court he did not seize the memory sticks from Williams's office because they contained information "of a sensitive nature" and the bag did not hold any information about his death.
"The bag was looked through and searched but nothing was seized. It contained work-related items, it contained personal items," said Hall.
The inquest previously heard how Williams would have suffocated within three minutes of getting inside the sports bag.
Pathologist Benjamin Swift said Williams probably died because of suffocation or an unknown poison which disappeared in his system during decomposition.