The Garda Onbudsman Commission was notified and attended the scene at an overnight incident in which a patrol car was involved in a collision with another vehicle close to the Barnesmore Gap.
Two people were brought to hospital, their injuries are not believed to be life threatening.
The road between Ballybofey and Donegal Town remains closed at Mc Groary's Brae, with traffic in Donegal Town being diverted at Lidl, and traffic from the Ballybofey side being diverted via the back roads over the Derg Line.
Gardai are looking for information about black Fiat Punto car seen driving towards Ballubofey from Donegal Town.
Information please to Letterkenny Garda Station at 91 67100 or the Garda Confidential Line 1800 666 111.