JACKSONVILLE, Florida (CNN)   -- Four people were killed and several injured after an explosion Wednesday at a chemical plant sent a thick plume of smoke over a section of Jacksonville, authorities said.

A thick plume of smoke rises Wednesday at a chemical plant in Jacksonville, Florida.

"Literally, it's a hellish inferno. There is no other way to describe it," said Fire Department spokesman Tom Francis.

Fourteen people were hospitalized after the blast at the T2 Lab on Faye Road, in an industrial area on the waterfront in north Jacksonville, Francis said.

Officials initially ordered an evacuation of nearby businesses, but by 4 p.m. the order had been lifted after tests of the air found no toxicity, Francis said.

Firefighters were still battling hot spots, and the effort will be going on for "quite some time," he said.  See an I-Report account about the blast »

Six of those injured were transported to Shands Hospital in Jacksonville, hospital spokeswoman Kelly Brockmeier said. A Shands official said the hospital incident command system had been activated -- something done to put the staff in high alert in anticipation of trauma patients.

A woman who answered the T2 Lab's 24-hour facility emergency phone said the plant manufactures ecotane, a gasoline additive that reduces tailpipe emissions, according to the laboratory's Web site.  See a map of the site of the explosion »

The billowing black smoke could be seen from the city's downtown, said Florida Times-Union reporter Bridget Murphy. Murphy said she talked to several workers as they walked out of the area, and they were "shaken to the core."

"They described a hissing noise and then a sound wave," she said.

Antonio Padrigan was trying to get in touch with his son, who works in a plant in the area, but was having no luck reaching him on his cell phone.

"He was shook up when he called me, but I can't get through to him anymore," Padrigan said. "I don't know if he's in the hospital or what."

CNN I-Reporters Jonathan Payne and his son Calvin, 16, shot pictures of the explosion. They felt the blast shake their home, about 15 minutes away, and went to see what was going on.

Carlton Higginbotham, 63, was working at home on Townsend Boulevard in Jacksonville when a loud boom shook his house, he said.

"It was a gunshot-type explosion; it wasn't a rumble," he said.

Higginbotham, an insurance salesman, and his neighbor ran outside and noticed thick smoke billowing from the other side of the St. Johns River, which separates his neighborhood from the site of the blast.

"The cloud that came out of it was white, some would say mushroom-shaped," Higginbotham said. "It was followed by dark, dark smoke." E-mail to a friend
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question: where firefighters are fighting?, answer: Jacksonville, Florida. | question: What did they say?, answer: "They described a hissing noise and then a sound wave," | question: What are firefighters fighting?, answer: an explosion | question: What did the official say?, answer: "Literally, it's a hellish inferno. There is no other way to describe it," | question: Who were taken to hospital?, answer: Fourteen people | question: which is the name of the spokesman for firefighters?, answer: Tom Francis. | question: What are firefighters still doing at the scene?, answer: battling hot spots, | question: Were many people hurt from the fire?, answer: Fourteen | question: When did the fire begin?, answer: Wednesday | question: What is happening now?, answer: Firefighters were still battling hot spots, and the effort will be going on for "quite some time," | question: what is it similar to?, answer: hellish inferno. | question: What number of people were hospitalized because of the fire?, answer: Fourteen | question: what caused the fire?, answer: explosion | question: Where did the injured people been taken to, answer: Shands Hospital in Jacksonville, | question: What did the spokesman say?, answer: "Literally, it's a hellish inferno. There is no other way to describe it," | question: What did the spokesman say to the reporter?, answer: describe it," | question: Who said that 14 people had been taken to hospital?, answer: Tom Francis. | question: In what city did the fire take place?, answer: Jacksonville, Florida. | question: What did spokesman tell reporters?, answer: "Literally, it's a hellish inferno. There is no other way to describe it," | question: what is the amount of people that have been taken to hospitals?, answer: Fourteen | question: What kind of description are fire officials giving the fire?, answer: hellish inferno. | question: What were the firefighters doing on Wednesday?, answer: still battling hot spots,