JACKSONVILLE, Fla. — Explosions and fires at a chemical plant yesterday 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, a fire rescue spokesman, Tom Francis, said.

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

Everyone at the plant was accounted for by yesterday evening. Hospitals reported one patient in critical condition, three fair and five good.

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 press reports and then hung up.

Fire officials initially ordered an 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 But the order was rescinded just after 4 p.m. when firefighters determined that the level of toxicity in the air was no greater than an average house fire, Mr. Francis said.