Gardaí are appealing for information.
More than 140 sheep were burned alive in the blaze which broke out on in a shed at Drumbuoy, Lifford on Sunday, reports the Irish Times.
Gardaí and a number of fire service tenders rushed to the scene but the blaze had already taken hold when they arrived.
It's reported there was also a large number of flammable hay bales in the structure.
Investigations into the possible cause of the fire are ongoing and anyone with information or who saw anything in the St Jude’s Court area of Lifford just before 1pm on Sunday is asked to contact Lifford Garda station on (074) 914100.
