A large explosion and fire at a chemical plant in Geismar, Louisiana, has killed one person and injured 73 people, authorities have said.
Authorities ordered people within three kilometres of the blast at the Williams Olefins chemical plant on Thursday to stay indoors after the blast at 8:37 a.m. (1337 GMT) sent a huge fireball and column of smoke into the air.
The fire, fueled by the petrochemical propylene, was still burning more than five hours later, although government monitors had yet to detect dangerous levels of emissions, Louisiana Governor Bobby Jindal told a news conference near the scene.
"There are no early detections of dangerous levels of VOC - that's volatile organic compound - but out of an abundance of
caution both the company and the DEQ (Department of Environmental Quality) are doing testing not only at the plant
site but miles away from the plant site following the direction of the plume," Jindal said.
About 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.
Parent group Williams Cos said that emergency shut-down valves had been closed and the unit isolated.
At least five victims were being treated at Baton Rouge General Hospital, Dr Floyd Roberts said.
"The next 48 to 72 hours is a critical time for burn victims, and as a team we're focused on stabilising airways, replacing fluids ... and treating the wounds with antibacterial dressing to combat infection," Roberts said.
The plant produces about 1.3 billion pounds of ethylene and 90 million pounds of polymer grade propylene, according to the Williams website. These are used in the petrochemical process to make plastics.
Southern Louisiana is home to a large share of the US's petrochemical facilities and has seen at least two other blasts
in the past two years.
Pressure on the industry to improve safety has increased since a blast at the Texas City refinery killed 15 people in 2005, among the worst such industrial accidents in decades.
A blast last month at a fertiliser plant in West, Texas, that killed 14 people has also sharpened attention on handling of volatile chemicals.