A ground-rattling explosion Thursday at a chemical plant in Louisiana ignited a blaze that killed one person and injured dozens of others, authorities said. Witnesses described a chaotic scene of towering flames and workers scrambling over gates to escape the plant.

“There was fire in excess of 100 to 200 feet in the air,” said state Sen. Troy Brown, who felt the blast at his house, less than five miles away. “It was scary to see.”

A thick plume of black smoke rose from the plant after the blast even after the fire was extinguished. At a roadblock several miles away where family members waited anxiously to hear about loved ones, flames were still easily visible above the trees even hours later.

Louisiana’s health department said 77 people were treated at hospitals, with 51 being released by the evening. Hospitals reported that workers mostly had burns, cardiac and respiratory issues and bruises, health department spokeswoman Christina Stephens said in a news release.