A ground-rattling explosion at a chemical plant in Louisiana early today (NZ time) ignited a blaze that killed at least one person and injured dozens of others, authorities said.
Louisiana's health department said 73 people were treated at hospitals for injuries ranging from minor to critical following the explosion.
State police Captain Doug Cain said a body was found by hazardous materials crews going through the aftermath of the blast at the facility owned by The Williams Companies Inc, based in Tulsa, Oklahoma.
Cain said all of the plant's more than 300 workers had now been accounted.
The company said the blast happened at 8.37am (1.37am today, NZ time) at the plant in an industrial area of Geismar, a Mississippi River community about 32km southeast of Baton Rouge. The cause was not immediately known.
The FBI said terrorism was not suspected.
A few homes and four other plants are within 3.5km, said Lester Kenyon, spokesman for Ascension Parish government. The Williams facility is one of scores of chemical and industrial facilities that dot the riverside between Baton Rouge and New Orleans.
A contract worker, Daniel Cuthbertson, 34, described a scene of "mass hysteria" immediately after the explosion, with workers scrambling over gates to get out of the plant.
"God was with me today because I know when I looked back, I barely made it. I know somebody was hurt. There's no way everybody escaped that," said Cuthbertson, who was interviewed at an emergency staging area about 4km from the plant.
State Senator Troy Brown said the ground shook at his house, several kilometres from the plant.
"It felt like a three-second earthquake. It was a massive explosion," Brown said.
He drove to a nearby gas station and saw flames 30-60-metres high.
"It was scary," he said.
Officials at area hospitals said a handful of patients were in critical or serious condition, though most seemed to have minor injuries.
Early tests did not indicate dangerous levels of any chemicals around the plant after the blast, but Cain said air monitoring continues.
Seven fire departments responded, Kenyon said.
Cain said the fire was out, but gas was being flared - burned at the top of high chimneys - in other parts of the plant. "There is still some controlled flaring going on, so people in the area are going to see smoke," he said.
Authorities said the plant makes ethylene and propylene - highly flammable gases that are basic building blocks in the petrochemical industry.
A thick plume of black smoke rose from the plant after the blast. In the early hours after the explosion, at a roadblock several kilometres away, where family members waited anxiously to hear about loved ones, flames were easily visible above the trees.