The blaze at a century-old firehouse in Manhattanville was likely sparked by an electrical source, fire officials said Saturday.

Assistant Chief James Esposito said the fire did not appear to be suspicious.

"This is definitely accidental," he said outside the firehouse on W. 139th St.

The home of Engine 80 and Ladder 23 caught fire about 7:30 p.m. Friday while firefighters were on a run. There was no one inside the building.

It took 25 units a little more than an hour to get the fire under control. Eight firefighters were injured, none seriously.

Fire marshals were investigating yesterday as firefighters were rerouted to nearby firehouses.

Deputy Chief James Nichols of the Bronx said though it was not the first blaze at a firehouse he has seen in his 30 years of duty, it was the worst.

"It's usually not a firehouse that's on fire," he said. "That's not why we call it a firehouse."