Britain's top police officer says spies will be asked to give DNA samples in a bid to solve the mystery of an agent whose body was found padlocked inside a sports bag in his bathtub.
Last week an inquest concluded that Gareth Williams had probably been killed by another person in a "criminally meditated act."
Coroner Fiona Wilcox was critical of the MI6 spy agency, which failed to pass evidence to investigating police.
Williams, 31, worked for Britain's GCHQ eavesdropping service. He was attached to MI6 when his remains were found in August 2010.
Metropolitan Police Commissioner Bernard Hogan-Howe said on Tuesday that detectives would conduct voluntary mass DNA screening of MI6 employees.
He said police needed to ensure "all areas of his life were fully explored."