Four staff members at Northern Ireland Police Ombudsman Nuala O'Loan's office are at the centre of a criminal investigation, it emerged today.
Detectives are investigating allegations a colleague made against them, and a former employee.
The inquiry relates to a shooting incident involving a police officer in Co Antrim nearly five years ago.
Senior staff at the agency, which was set up under the Belfast Agreement to examine allegations of police wrongdoing, are under investigation.
A spokesman for Mrs O'Loan, who is not under investigation, refused to disclose any more details.
"The police have launched an investigation into criminal allegations made by a member of staff at the Police Ombudsman's Office against a number of his colleagues.
"They relate to a court case arising from the discharge of a firearm by a police officer in Newtownabbey in June 2001.
"The four staff are at both senior and junior levels within the Police Ombudsman's Office." The spokesman also pledged full co-operation with the inquiry.
The PSNI confirmed the inquiry was under way but would not make any further comment but
source close to the investigation revealed it had been ongoing for four to five weeks.
"The Ombudsman's Office is fairly relaxed about this," he added.
Ian Paisley Jr, a Democratic Unionist member of the Northern Ireland Policing Board, said: "This is a most bizarre turn of events. Here we have the investigators being investigated by those they are supposed to be looking at.
"It also calls into question the nonsense that we have in Northern Ireland of so many people in oversight whenever the public wants to see criminals investigated and justice delivered."