A memory stick containing sensitive information about on-going police operations has been stolen, a force said today.
It was taken during a burglary at the home of a serving officer for Greater Manchester Police (GMP).
The force said a dedicated team of officers is working to identify the burglars and recover the storage device.
Assistant Chief Constable Garry Shewan said GMP had contacted one member of the public whose personal details were among the information on the memory stick.
He added: "I want to reassure residents across Greater Manchester that we are taking this incredibly seriously and we are working hard to both identify who was responsible for the burglary and recover the stolen memory stick.
"I want to stress that we do not believe the officer's home was deliberately targeted, but that this was an opportunistic burglary.
"I also want to make it clear that any suggestion this memory stick contained lists of names of people who 'tipped off' police is inaccurate.
"We know what is on the device because the officer has told us, and so far we have only had to speak to one member of the public whose personal information may have been compromised."
The burglary took place in the Oldham area on July 17.
GMP is appealing to anyone who finds the red and orange memory stick to call police immediately or hand it in to their nearest police station.
A black Volkswagen Gold, registration number MJ58 JVX, was also stolen during the burglary and police are appealing to anyone who knows of its whereabouts to come forward.
Mr Shewan said the force was conducting a review of how sensitive information is stored.
"Any information that relates to Greater Manchester Police is considered sensitive so it is important we recover it as soon as possible," he said.
"Greater Manchester Police is reinforcing to officers and staff the importance of keeping information secure at all times.
"We expect all officers and staff to adhere to rigorous standards with regard to confidential and sensitive documents."