A section of the N15 has been closed in the area near the Roadhouse Bar, which is about a mile outside Ballybofey.
The main road out of Ballybofey to Barnsemore Gap is closed and diversions are in place.
Gardai have said that there is no access to Barnesmore Gap from Ballybofey due to the RTC.
Traffic travelling from the North of the county towards Donegal Town/Sligo is being asked to divert via Glenties.
While traffic travelling from the South of the county to the North of the county are asked to divert via the Derg line.
While lorries travelling from the South of the county are asked to divert via Glenties as the Derg line cannot hold the weight of certain vehicles.