Firefighters come down from the roof of the Allegheny Valley School in Slippery Rock on Wednesday. They responded to a report of a fire at AVS at 12:50 p.m. A malfunctioning heating unit caused smoke to circulate in the school on Rebecca Lane. There was no damage to the roof, but firefighters were called to determine the source of the smoke, said Ken Taggart, chief of the Slippery Rock Volunteer Fire Department. Staff and students were out of the building when firefighters arrived. One firefighter suffered a minor injury. Grove City, Pine Township, Unionville and Harrisville volunteer fire departments assisted. They cleared the scene after about 90 minutes.