When she finally tracked Harold Daubs down at an area firehouse, he was in a state of shock, having helped carry two injured co-workers to safety.

"He's just getting out of bed now," she said late Sunday morning. "He's traumatized."

Four workers were killed and eight others injured in the explosion at the Formosa Plastics plant Friday night, which authorities said happened as workers mixed vinyl chloride and vinyl acetate.

The cause of the explosion was under investigation Sunday. Firefighters were still trying to put out fires Sunday afternoon, said Sangamon County Sheriff's Department Sgt. Joe Rath.

Two in critical condition

Four workers remained hospitalized Sunday at Memorial Medical Center in Springfield. Two were listed in critical condition, one in serious condition and one in fair condition, a nursing supervisor said. Daubs and five others escaped without injury.

Carolyn W. Merritt, chairwoman of the U.S. Chemical Safety and Hazard Investigation Board, said the explosion was the most serious the agency has responded to in more than a year. She said vinyl chloride and vinyl acetate are both highly combustible materials.

"You're not going to be doing this (mixing the two chemicals) in your basement," she said.

The explosion forced the evacuation of Illiopolis' roughly 1,000 residents because of hazardous fumes from the burning plant. When vinyl chloride burns it emits hydrochloride, which is toxic, authorities said.

Preliminary tests indicated the air was safe to breathe, authorities said. Residents have been given the OK to return home, said Becky Rohdemann, a clerk with the plant.

The plant makes PVC resins that are used in vinyl flooring, traffic cones and carpet backing, said Rob Thibault, a spokesman for the plant's corporate parent.

On Sunday, the plant's administrative office was back in operation.

"We're functioning in the front office, but everywhere else is a disaster," Rohdemann said. "There's a lot of cleanup to do."

Harold Daubs was one of several employees in area of the plant nicknamed "the lab" at the time of the blast. His wife said he hid underneath a table when the explosion knocked out a nearby wall and sent debris flying.

"There was a tunnel and he just crawled in, and then he heard the other guys screaming," she added.

That's when 62-year-old Harold Daubs and another man began pulling rubble off of their injured co-workers. As fires raged nearby, Harold Daubs pulled two men to safety.

"The old adrenaline kicked in," Judy Daubs said.

One of the workers Daubs carried out was 51-year-old Chris Havener, who was in serious condition at Memorial Medical Center. His brother, Todd Havener, said he sustained a broken arm, a broken leg and burns.

"He got his injures from a masonry wall being blown out ... it just buried him up," Todd Havener said.