COOPERSTOWN (AP) - Fire has heavily damaged a restaurant in the eastern North Dakota town of Cooperstown.

Griggs County Sheriff Bob Hook says the alarm at the Post Office Restaurant was triggered shortly before 5 a.m. Thursday.

The Fire Hall is right across the street, and Hook says a quick response by firefighters probably saved neighboring businesses connected by common walls.

No one was hurt. It took firefighters about an hour to extinguish the blaze. The cause isn't known, though Hook says authorities suspect the restaurant's air conditioning system might have been the source.