The American Zinc Products plant in Mooresboro, North Carolina, forced evacuation within a half-mile as a fire poured deadly acid into the surrounding air.

“The concerns are not necessarily the zinc. The concern is that sulfuric acid has been released,” Rutherford County Assistant Fire Marshal John Greenway told Fox Carolina on Monday morning. “We’ve had the decontamination firemen out here, and their gear tested positive as hazardous.”

Sulfuric acid, also known as battery acid, is an extremely corrosive substance capable of burning through metal almost as easily as tissue.

Greenway said an evacuation shelter had been established at Chase Middle School. Later in the morning, Superintendent Janet Mason said the shelter had been relocated to the Chase High School auxiliary gymnasium. Just under 50 residents were affected by the evacuation.

The cause of the fire remains unknown, though as of the time of this writing, it has been fully extinguished. Capt. Bill Greene of Ellenboro Fire Department said that the 75-foot-high inferno was fought by 100 different brave first responders from 15 different surrounding firefighting crews. Aside from clouds of acid, they further contended with at least a dozen explosions.

In response, American Zinc Products released this statement:

We applaud the courageous efforts of the fire departments in fighting this blaze. They have successfully contained the fire, with no injuries to any of our employees, who have all been accounted for. We are cooperating fully with state and local authorities to investigate the causes of the fire. Our highest priority at all times is to protect the community, our employees and the environment and we are grateful to the quick action by the local first responders. We are unable to comment further at this time.

An investigation into the source of the blaze will commence as soon as the area has been deemed safe enough to approach.