The fire was reported shortly after 6 p.m. at Evraz Claymont Steel Company, formerly CitiSteel, in the 4000 block of Philadelphia Pike as a fire in the melt shop, Chief Deputy State Fire Marshal Alan Brown said.

Investigators determined that the fire started in an electric arc furnace.

The carbon brick insulation in the furnace separated from the wall, allowing the molten liquid steel to burn through the wall liner, Brown said.

The molten steel ignited nearby combustible materials and hydraulic fluids, heavily damaging the unit.

The injured worker was on a crane above the container with the molten steel and could not get free without help.

Firefighters had to use ropes to rescue him because there was no visibility in the room.

The crane operator was taken to Crozer Chester Hospital’s emergency room, where he was treated and released.

The situation was placed under control about 7:26 p.m.

More than 20 employees had to be evacuated from the plant.