Firefighters and Maritime Electric crews investigate the substation shortly after the April fire. (CBC)

The fire at a substation outside Charlottetown that knocked out power to half of P.E.I. at the end of April was caused by a squirrel, says Maritime Electric.

The squirrel got into the West Royalty substation and gnawed on some wires. The resulting fire eventually led to 55,000 customers being without power and caused $200,000 worth of damage.

"Normally a squirrel wouldn't be able to do that type of damage, maybe a circuit or two, and a small outage, but … we [also] actually had a failure of a piece of equipment," said Maritime Electric spokeswoman Kim Griffin.

"The investigation is still underway in that we're still trying to figure out which happened first."

Griffin said the utility has learned some lessons from the experience, and will be tightening up rodent control at its facilities.

"In some areas where there may be an opening, or anyone who has had problems with even squirrels in their own home, they know the damage that occurs once they get inside," said Griffin.

"It appears that the squirrel was inside, we're not sure for how long, but in terms of being able to get in and do a substantial amount of damage on our wires, it was that as well as a system failure itself."

The April 27 blackout across the eastern end of the Island started at about 9:20 a.m. and lasted several hours. Power began to be restored by early afternoon, but 2,000 customers did not have their power back until early the next day.

Maritime Electric was able to confirm the squirrel caused the blackout when it recovered the animal's remains. The condition of the remains was described as "not good."

This is not the first major blackout reported to be caused by a squirrel this year. In mid-April, a squirrel getting into equipment in Whitehorse was blamed for a blackout across the southern Yukon.