An explosion and fire killed at least one person and injured 33 at the Williams Olefins chemical plant in Geismar, Louisiana, on Thursday, leading authorities to order people within two miles to remain indoors.
The blast created a huge fireball and column of smoke when it hit at 8:37 a.m. (0937 ET) at the plant along the Mississippi River just south of Baton Rouge and about 60 miles up river from New Orleans.
About 600 people were working at the plant at the time, and the fire was still burning more than three hours later, state police said.
A body was recovered at the explosion scene and a search continued for more possible victims, Louisiana State Police Captain Doug Cain said.
The blast injured 33 people, said Jean Kelly, a spokeswoman for the Louisiana Department of Environmental Quality. Thirty were taken from the plant by ambulance and three by helicopter, Kelly said.
"Emergency shut-down valves have been closed. The unit is isolated," parent group Williams Cos. said in a statement. "We are in the process of accounting for all personnel."
Authorities ordered people within a 2-mile (3-km) radius to remain in their homes, in part because of the toxic smoke, said Lester Kenyon, a spokesman for Ascension Parish. Roads leading to the plant were closed, the company said.
The U.S. Coast Guard said traffic on the Mississippi River remained unaffected.
"It's an active scene. The fire department, the sheriff's office and hazmat (hazardous materials) team are responding to the explosion at the Williams Olefins plant," said Amy Johnson, a spokeswoman for the Ascension Parish Office of Homeland Security and Emergency Preparedness.
The company's own emergency response crews were assisting at the scene, Williams said.
The plant produces approximately 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.
"The chemical involved is a flammable, which is good in the sense that it is burning itself off, so there's no impact outside the fence line of the facility," Cain said.
Williams operates the plant and holds an 83 percent ownership interest in the Geismar facility, it said.
Shares in Williams Cos. fell as much as 3 percent shortly after the reports and were down about 1 percent in early afternoon trade.
With massive equipment operating under intense pressure and high heat, the petrochemical industry is particularly prone to occasional fires and explosions, most of which are quickly brought under control with limited injury or damage.
Southern Louisiana is home to a large share of the country'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 fertilizer plant in West, Texas, that killed 14 people has also sharpened attention on handling of volatile chemicals.