Daniel Cuthbertson knows the risks involved in working at chemical plants.

Still, the Taft, Calif., contract worker who travels frequently for such work was rattled hours after escaping Thursday's blast at a south Louisiana plant. The explosion killed at least one worker and sent dozens to area hospitals, some with critical injuries.

"I'm still shaken," he said. "I'm thinking about my kids, kind of taking a personal inventory of everything."

Cuthbert said the blast sent workers on a mad scramble to escape the plant, some of them by clambering over gates. Outside the plant, witnesses saw towering flames and felt the ground shudder.

A body was found by hazardous materials crews moving through the site after the blast, state police Capt. Doug Cain said. Police identified the man killed as 29-year-old Zachary C. Green, of Hammond.

Louisiana's health department said 77 people were treated at hospitals and 51 of those had been released by Thursday evening. Hospitals reported that workers mostly had burns, cardiac and respiratory issues and bruises, health department spokeswoman Christina Stephens said in a statement.

At nearby Dutchtown High School, football players were in offseason conditioning on a playing field when they heard the boom. Students rushed inside and the school went into emergency lockdown.

"Our school system does a real good job of training us for these types of things, lockdown and having water and paper towels and all the stuff you would need to survive if you have to stay inside for a long period of time," coach Benny Saia said in an interview after the lockdown was lifted.

"There was fire in excess of 100 to 200 feet in the air," said state Sen. Troy Brown, who felt the blast at his house, less than five miles away.

"It felt like a three-second earthquake. It was a massive explosion," added Brown. Unsure what it was, he drove to a gas station down the street from his house and saw the huge flames shooting skyward.

The Williams Companies Inc., which owns the plant, said the blast occurred at 8:37 a.m. By the afternoon, all of the plant's more than 300 workers had been accounted for, Cain said.

The plant is in an industrial area of Geismar, a Mississippi River community about 20 miles southeast of Baton Rouge. It's one of scores of chemical and industrial facilities dotting the riverside between Baton Rouge and New Orleans.

A few homes and four other plants are within 2 miles, said Lester Kenyon, spokesman for Ascension Parish government.

The cause was not immediately known but the FBI said terrorism was not suspected.

More than 300 people were evacuated from the site, but some stayed behind, officials said. Ten workers stayed in an explosive-proof control center as the fire raged, Cain said. The workers performed vital tasks, including shutting valves that rendered the plant safe, he said.

Officials at area hospitals said a handful of patients were in critical or serious condition, though most seemed to have minor injuries.

The plant makes ethylene and propylene -- highly flammable gases that are the basic building blocks in the petrochemical industry.

Early tests did not indicate dangerous levels of any chemicals around the plant after the blast, but Cain said air monitoring continued Thursday afternoon.