A number of buildings on the town’s Main Street including the local courthouse have been left without lighting.
It is understood the ESB are working to rectify the situation.
A faulty transformer is understood to be the cause of the outage.
A spokesman for the ESB has said that a major fault in the Gortleee/Letetrkenny and Manorcunningham areas has led to the disruption.
No details of when the power will return have been released.
A number of businesses have been unable to operate since the outages.