An explosion and fire killed one person and injured 73 at the Williams Olefins chemical plant in Geismar, Louisiana, on Thursday, June 12, unsettling an industrial town where authorities ordered people to remain indoors for hours to avoid the billowing smoke, Reuters reported.

The blast at 8:37 am (0937 ET) sent a huge fireball and column of smoke into the air. The plant along the Mississippi River, about 60 miles from New Orleans, is one of 12 chemical plants along a 10-mile (16-km) stretch of the river.

The fire, fueled by the petrochemical propylene, burned for more than three hours, though government monitors had yet to detect dangerous levels of emissions, Louisiana Governor Bobby Jindal told a news conference near the scene.

Some 300 workers from the plant were evacuated and all the employees were accounted for, among them 10 who stayed behind in a safe room inside the plant, Jindal said.

The plant produces approximately 1.3 billion pounds (590 million kg) of ethylene and 90 million pounds (40 million kg) of polymer grade propylene per year, which are used to make plastics.