LEETSDALE (KDKA) — Three workers were injured in a steam explosion at a plant in Leetsdale.

The workers were in the casting area of Hussey Copper when the accident happened at about 9:40 a.m. Tuesday.

“They’re making large ingots out of copper and during the cooling process, water possibly got into a spot that it wasn’t supposed to and subsequently had a back flash and burned the three victims,” Leetsdale Police Chief Jim Santucci said.

Investigators say the three men were wearing fire-retardant suits, but were injured despite the protective gear.

“Upon arrival, we found two stable enough to be transported by ground. The third victim had 20 – 25 percent of his body burned,” Santucci said. “Therefore, we had to Stat MedEvac him to Mercy[‘s] burn unit.”

The worker taken to UPMC Mercy remains in the hospital. The other two victims were treated at Allegheny General Hospital, released and returned to work.

Company officials say there was minor property damage, but it did not disrupt operations.

The cause of the fire is still under investigation.