The Associated Press

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

JACKSONVILLE, Fla. — Hazmat teams worked to stamp out flare-ups Thursday in the remains of a chemical plant where an explosion and fire killed four people and injured at least 14.

A U.S. Chemical Safety Board team was expected to arrive Thursday morning at the T2 Laboratories Inc. plant to investigate.

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

The names of the victims have not been released.

The company's voicemail was full Thursday and did not accept phone messages. A message left on T2 Laboratories' emergency line was not immediately returned.

"Nothing there resembles a building," Mayor John Peyton said Wednesday. "It's amazing when you see the scene that there wasn't more loss of life."

It was not clear what caused the explosions Wednesday at the plant, which makes chemical solvents and fuel additives, said Tom Francis, a fire rescue spokesman. Firefighters determined the level of toxicity in the air was no greater than an average house fire.

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."