Three gardaí were treated in hospital on Friday night after a patrol car was struck by another vehicle at 3.30am.
The incident happened on Ramelton Road, Letterkenny. There are additional gardaí on duty in the town for the the Donegal International Rally taking place this weekend.
The driver of the car that struck the patrol car, a 17-year-old, was arrested at the scene under the Road Traffic Acts and taken to Letterkenny Garda Station. He was later released without charge.
The three gardaí were treated at Letterkenny University Hospital for minor injuries.