Detectives investigating the suspected theft of sensitive security documents from the office of Northern Ireland's Police Ombudsman have arrested a man in England.
The 69-year-old is understood to be a former ombudsman investigator.
He was detained on Sunday and has since been released on bail.
As part of its role probing alleged police misconduct, ombudsman investigators can access classified documents from the PSNI.
The information sharing has been temporarily suspended in the wake of the alleged security breach.
Assistant Chief Constable Stephen Martin, head of the PSNI's Crime Operations Branch, said: "The PSNI can confirm it has become aware of a suspected theft of sensitive documents from within the Office of the Police Ombudsman of Northern Ireland.
"We have now commenced a criminal investigation and are also carrying out an assessment of any impact which may be caused by the unauthorised release of sensitive material.
"Detectives from our Serious Crime Branch conducted a joint search operation with Kent Police on Sunday and arrested a 69-year-old man in Dartford, Kent, in connection with the matter.
"The PSNI and PONI have agreed to a temporary period of review during which sensitive information will not be shared."