WEST PARIS, Maine — Crews spent nearly five hours Monday battling a fire that torched at least 20 vehicles stacked in a scrap metal yard on Maple Street.

One firefighter suffered a back sprain and was taken to a hospital, an official said.

Ernie Yap, owner of West Paris Metals, said he was unsure exactly what started the fire. One of his employees was using either a saw or a torch to cut apart some of the junked vehicles, preparing to move them from the site, he said.

Reportedly, a spark ignited one of the vehicles, and the fire quickly was out of control, Yap said. Usually, two employees work together when cutting up vehicles, he said, but only one was working at the yard at the time.

Fire crews were called to the scene at about 3:30 p.m. Firefighters from West Paris, Paris, Norway, Oxford, Greenwood and Woodstock initially responded and were later joined by crews from Buckfield, Turner, Canton and Gilead.

Noxious plumes of black smoke billowed more than 100 feet in the air, and small explosions were heard as the fire ate its way through scrapped vehicles stacked at the western end of the yard at 36 Maple St.

As of 8 p.m. some crews were still on the scene making sure the fire was out.

West Paris Fire Chief Norm St. Pierre could not be reached for comment Monday night, but Norway Fire Chief Dennis Yates, who responded to the scene, said remaining firefighters were pulling cars apart to extinguish flames.

The intense heat of the blaze, as well as the day’s high temperatures and direct sun, required additional manpower so firefighters could be regularly cycled off the front line to prevent heat stroke and dehydration, Yates said.

Maine Department of Environmental Protection responded to the scene, Yates said.

One firefighter was transported to Stephens Memorial Hospital because of a back sprain, but otherwise no injuries were reported, Yates said.