An overnight fire severely damaged a building on the north side of Oskaloosa’s downtown square, Jefferson County emergency officials said.

The fire was discovered about midnight by a Jefferson County sheriff’s deputy who was on patrol. Oskaloosa firefighters responded and called for assistance from several surrounding fire departments, Sheriff’s Lt. Rick Jones said.

The building is owned by Karl Swoyer. It housed two businesses, PIA Friend Realty and His & Her Hairstyling.

An electrical problem is thought to have caused the fire, Jones said.