Gardai have not ruled arson in a fire which rage through an old school building in Ballyshannon.
Four fire units from the town, Bundoran, Donegal town and Letterkenny, fought the blaze for four hours last night.
The street around the area was closed while fire personnel were battling the blaze in the Old Sacred Heart school.
Gardai said a substantial amount of damage was caused. Nobody was injured.
Scenes of crimes officers were examining the scene today. A Garda spokesman said they were trying to establish the source. They had not ruled out arson.
The building has been closed for years to the public.