It is the latest in a series of data breaches that may endanger the lives of police officers in Northern Ireland.

A laptop and notebook fell from a police car on the M2 motorway in north Belfast at around 4.15pm on Thursday.

"The laptop was immediately deactivated and has since been recovered. No personnel files were involved," assistant chief constable Chris Todd said.

"A significant amount of the notebook has since been recovered. Some sections remain outstanding and our inquiries are continuing to establish the contents.

"It was confirmed that some of the outstanding pages, which contained details of some officers and staff, have not yet been recovered," he added.

"We have contacted those involved to make them aware.

"Forty-two officers and staff have been specifically identified as being affected and directly contacted last night by line managers and senior management.

"In addition, the entire branch affected has been informed about the circumstances of the incident.

"We are liaising with the Office of the Information Commissioner and have advised the Northern Ireland Policing Board and the Department of Justice."

It comes just a week after the PSNI confirmed the personal details of more than 10,000 officers and staff were mistakenly published online in response to a freedom of information request.

Details released included the surname and first initial of every employee, their rank or grade, where they are based, and the unit they work in.

On Monday, PSNI Chief Constable Simon Byrne said he believed the information was in the hands of dissident republicans.

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It followed the posting of documents from the leak on a wall near a Sinn Fein office in Belfast.

In a separate incident, also confirmed last week, a document containing the names of officers and staff was stolen along with a police-issue laptop from an officer's car on 6 July.

Many officers have expressed concern for their safety in Northern Ireland, where police are under threat from terrorists - with the current level of threat assessed as severe, meaning an attack is highly likely.