Two workers are dead and one remains in critical condition after a U.S. Steel plant explosion Sunday in Fairfield, Alabama.

Edward Lamar Bryant died from burn complications Sunday after the explosion. Leo Bridges was taken off life support Tuesday morning and was pronounced dead at 10:34 a.m. Mac Bedwell remains critical at UAB Hospital’s Trauma and Burn Intensive Care Unit.

According to reports, the workers were injured when a pipe exploded in the Q-BOP, a basic oxygen process furnace where molten steel is made. The cause of the blast hasn’t yet been determined.

“An investigation into the incident is underway,” according to a statement from U.S. Steel. “Fairfield Works is operational. No further details are available at this time.

The steel plant, located 10 miles west of Birmingham, can produce 2.4 million tons of steel annually and employs 1,700 workers.