A distribution plant carrying highly flammable gases went up in a fireball on Monday outside of Charleston, West Virginia, injuring two people.

The fire at Airgas involved 50 tanks of acetylene which were about to be refilled, said fire officials. An investigation is pending to determine what caused the explosion, but witnesses say once the first tank went, the others followed quickly, creating fireballs that shot over 100 feet in the air.

“We felt our building shake like it’s never come close to shaking before from a storm or anything. It was enough to make us run,” said Doug Barker, who works at a nearby business.

Fortunately, the explosions occurred in a concrete-enclosed area away from the main plant and the tanks weren’t full; otherwise, there might have been many more injuries. For now, the fire is put out, but a HAZMAT crew has been sent from Kentucky to secure the area. The plant specializes in several different gases, including the acetylene, which is used for welding, as well as propane, hydrogen, helium, and nitrous oxide.

The injured workers suffered second and third-degree burns, but their condition is not known at this time.