A man remains in hospital in a serious condition following an overnight crash on the Letterkenny to Ballybofey road at Drumkeen.
The two vehicle collision occurred at around midnight.
A man in his late teens is in a serious condition in hospital. Two other people involved in the crash also suffered injuries.
The road remains closed to facilitate an investigation - diversions are in place.
Gardai expect the road to re-open around 4 o'clock this (Thursday) afternoon.