Vandalism to the insulators at the Virginia Waters substation caused this morning's outage that affected customers for several hours in the east end of St. John's, Newfoundland Power says.
It's not yet clear how the insulators were damaged.
Newfoundland Power is calling in the Royal Newfoundland Constabulary to investigate.
Power was knocked out in parts of the east end, especially around Wedgewood Park and the King William Estates areas, around 7:30 a.m.
Newfoundland Power said vandals damaged more insulators than the ones that failed, triggering the outage, and that all of them will need to be replaced.
An official said it appears that the insulators were hit by something.
Lights also flickered across much of the northeast Avalon.
A caller to CBC News said she saw flashes and then smoke at a substation on Snow's Lane, near the Stavanger Drive neighbourhood.