STORM LAKE, Iowa | Authorities are investigating a Saturday night fire that damaged the Hillshire Brands turkey processing plant in Storm Lake and took about 18 hours to extinguish.

No civilian injuries were reported. However, a Storm Lake firefighter suffered a shoulder injury and was treated and released at Buena Vista Regional Medical Center, according to a statement from the Storm Lake Department of Public Safety.

At about 7:15 p.m. Saturday, Storm Lake firefighters responded to an automated fire alarm and discovered “heavy black smoke and flames” coming from the plant’s production area roof, the statement said.

A roughly 50-by-50-foot section of roof had burned and collapsed, while the rest of the building sustained substantial fire and smoke damage. A cost estimate of the loss was not available.

With help from fire rescue teams in Alta, Newell and Sioux Rapids, more than 50 firefighters had the fire under control in about three hours. Storm Lake firefighters remained on the scene as small spot fires continued to flare up until about 1:15 p.m. Sunday, said Public Safety Director Mark Prosser.

The Iowa State Fire Marshal’s Office will begin its investigation into the fire’s cause Monday, Prosser said. It is expected to take several days.