A fire Thursday night damaged a house in the northern part of Fort Smith.

The fire, which firefighters with the Fort Smith Fire Department responded to at 11:45 p.m. Thursday, significantly damaged a vacant 2½-story house in the 300 block of North 20th Street. Though fire officials do not yet know the cause of the fire, neighbors told officials they had seen people go in and out of the vacant house and that someone was possibly squatting inside, chief Tommy Bishop with the Fire Department said Friday.

"There wasn't supposed to be anybody in there, but we're kind of thinking otherwise," Bishop said.

Bishop on Friday did not give a damage cost estimate for the structure.