The Associated Press

AP Photo/Bob Self Smoke can be seen Wednesday after the explosions.

JACKSONVILLE, Fla. — Explosions and fires at a chemical plant Wednesday killed four people, injured at least 14 and sent debris flying several stories into the air, fire officials and witnesses said.

It was not clear what caused the explosions about 1:30 p.m. at the T2 Laboratories Inc. plant, which makes chemical solvents and fuel additives, said Tom Francis, a fire rescue spokesman.

The chemicals at the plant made the environment "incredibly dangerous for the first responders," Francis said. "Explosions were generating all kinds of side brush fires and other kinds of blazes."

Everyone at the plant was accounted for by Wednesday evening.

Hospitals reported one patient in critical condition, three fair and five good. Conditions for the rest were unknown, or it wasn't clear where they were being treated.

An emergency number listed on the company's Web site was answered by a woman who said she was an owner's friend. She said the only details she had were from media reports and then hung up.

Fire officials initially ordered a precautionary evacuation within a half-mile of the plant. But the order was rescinded just after 4 p.m. when firefighters determined that the level of toxicity in the air was no greater than an average house fire, Francis said.

A board member and a six-person investigation team from the U.S. Chemical Safety Board was expected to arrive at the site Thursday morning to begin an investigation.

Derek Pratt, 24, was flying a remote control airplane at a field about a mile away when he heard a series of thudding explosions.

"Those shock waves came straight through these hills," he told The Florida Times-Union. "It was like a great ball of fire in the air."

The fire was across the street from a JEA power plant, a spokeswoman with the utility said.