ALLENSVILLE, Pa. (WHTM) — Investigators are working today to determine what caused a blaze that the fire chief here called the worst he had ever seen.

It happened at Allensville Planing Mill in western Mifflin County. The building where the company makes trusses appeared to be a total loss. A True Value hardware store at the site survived. The mill dates to 1959, according to its website. Remains of the building were still smoldering 15 hours after the fire was first reported at about 9:30 p.m. Tuesday night.

Lynn Fleming, chief of Allensville’s volunteer fire department, called the support his department received from Mifflin and surrounding counties “exceptional.” Asked how many engines had responded, he said he lost count after 10; someone had counted 22 tankers brought in to fight the fire, he said.

Fleming said Pennsylvania State Police, assisted by a fire marshal, are investigating.