Maine ? Investigators say a fire that swept through a historic textile mill in Maine’s second-largest city was a case of arson.

Maine Public Safety Department spokesman Steve McCausland says fire marshal investigators reached the conclusion working with Lewiston police and fire officials and investigators from the federal Bureau of Alcohol, Tobacco and Firearms. The ATF is offering a $5,000 reward for information leading to an arrest and conviction.

McCausland says there were reports of three young people running from the unoccupied Cowan Mill in Lewiston, but he says those haven’t been substantiated.

The 60,000-square-foot mill was built in 1850 and is on the National Historic Register. It overlooks the Great Falls on the Androscoggin River.