Prison officers were forced to provide security at an abandoned Stormont office block used to store personal information after a spate of recent break-ins.
It is understood a large number of Department of Justice files were being stored at Dundonald House, an abandoned office block in the grounds of the Stormont Estate in east Belfast.
The PSNI has confirmed that it received reports of “burglary and illegal trespass” at an office building on the Upper Newtownards Road, Dundonald “on a number of occasions” between March 16-20.
Footage of the interior of the building was later posted online, but has since been removed.
It has now emerged that the DoJ, which runs the Prison Service, was using a floor in the vacated building to store personal data, including the names and address of Prison Officers.
Officials have contacted the Information Commissioner’s office (ICO).
Sources say that while the intruders failed to gain entry to the floor where the material was being held, the incident has raised wider security concerns.
It is understood that in the days after it emerged there had been a series of break-ins at Dundonald House prison officers were sent to guard the building at night.
Prison Service staff were targeted by republicans during the Troubles and two serving officers have been killed by the New IRA since 2012, including David Black, who was shot dead as he drove to work at Maghaberry Prison in November that year.
In 2016 prison officer Adrian Ismay died in hospital 11 days after a bomb exploded under his van in east Belfast.
Data breaches by public bodies have caused security headaches in the past.
In 2023 the PSNI was pitched into a crisis when personal details of 10,000 staff members were accidently released.
It is believed all files, which were previously held in temporary accommodation before being moved to Dundonald House, have now been removed from the office block and transferred to a secure location.
The building was previously occupied by DoJ and according to a spokeswoman “has been vacant of civil service staff since June 2023 when it was closed for normal day to day operations due to a serious health and safety issue”.
However, speaking in the assembly last month justice minister Naomi Long told UUP MLA member Robbie Butler “some areas of Dundonald House remain in limited use” in response to an assembly question.
“For obvious reasons, I do not want to explain in public that use in any detail, but I can be absolutely clear that no sensitive or personal information has been compromised during those forays into the building,” she added.
A spokeswoman for the department added on Wednesday that it “has now fully vacated the building”.
“Although the incident did not meet the threshold for reporting as there was no breach of personal information, the Information Commissioner was notified,” she added.
A spokeswoman for The Department of Agriculture, Environment and Rural Affairs said it previously “part-occupied” Dundonald House.
Asked if it stores sensitive or personnel information in the building and if the burglaries presented any security issues, it did not answer directly.
The department was also asked if it contacted the ICO, but again, did not respond directly.
“There was no breach of the department’s data or information,” a spokeswoman said.
A spokesman for the PSNI said: “Entering grounds or buildings without the owner’s consent is both illegal and dangerous. Climbing up onto roofs and other high surfaces is wrought with danger.
“A young person could easily slip or lose their footing and end up with serious, permanent injuries or worse.
“Being caught inside a building without permission is burglary and could end with a visit to a Magistrates’ Court.
It is understood no arrests have been made.
A spokeswoman for the ICO said: “The Department of Justice reported an incident at Dundonald House to us but after looking into the details confirmed no personal data was accessed.”