The identities of thousands of Northern Ireland police officers were accidentally published online following a data breach, politicians and union officials said Wednesday.

An investigation has been launched into the release of the surnames and initials of all of its more than 9,000 current police and civilian employees with the location and department to which they are assigned that was mistakenly included in a Freedom of Information Request, Police Service Northern Ireland said in a news release.

The surname and first initial, service number, rank or grade and unit to which they are attached and its location were all visible on a well-known FoI site, as well as classified information detailing involvement in surveillance and intelligence, UPI reports.

Northern Ireland officers keep very low profiles, with some even withholding the fact they are in the police from their families and friends.

Officers have continued to be targeted, particularly by dissident republican paramilitaries, throughout the 25 years since the Belfast Good Friday Agreement that ended the three-decade-long "troubles."

More than 300 were killed in the Troubles and as recently as February a senior officer was shot by masked gunmen as he coached a youth soccer team.

All police officers in Northern Ireland carry firearms.