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

The blast at 8:37 a.m. (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.

A large fire burns at the Williams Olefins chemical plant in Geismar, Louisiana in this picture taken June 13, 2013.

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.

Emergency responders took 73 people to hospital, Jindal said, including at least five who were being treated at Baton Rouge General Hospital's burn center, said Dr. Floyd Roberts, a physician there.

The same plant had an accident in 2009 when about 60 pounds (27 kg) of a flammable mixture was released, resulting in a fire that caused property damage but no injuries, according to the Right-to-Know Network, citing data from the U.S. Environmental Protection Agency's risk management database.

An explosion at Geismar's Westlake Chemicals vinyl plant sent a cloud of toxic vinyl chloride and hydrochloric acid over the town in March of 2012, and in June 2011 there was an explosion at a Multi-Chem Group plant in New Iberia, about 50 miles from Geismar. Neither blast caused injuries.

Pressure on the industry to improve safety has increased since a 2005 blast at a BP refinery in Texas City, Texas, killed 15 people and injured 170 in one of the worst such industrial accidents in decades.

(Source: Reuters)