David Manning / Reuters PHOTOBLOG: Firefighters prepare to put out a container of burning caps as thousands of exploded propane cylinders litter the storage yard of a propane plant after massive explosions overnight in the plant's yard, in Tavares, Fla., on Tuesday. Click the image for more photos.

A combination of human error and equipment failure might have caused a series of explosions that engulfed a propane plant in flames in Tavares, Fla., late Monday, injuring eight people and forcing evacuations for a half-mile around the scene, authorities said.

The explosions began as a fire spread through the Blue Rhino plant, near Orlando, about 10:30 p.m. ET, Lake County sheriff's Lt. John Herrell told reporters early Tuesday.

Plant officials said all employees of the plant were accounted for. All of those injured were in the plant when the fire started.

Tavares Fire Chief Richard Keith said Tuesday morning that sabotage isn't suspected. The fire marshal was on site to do a full investigation.

Keith told reporters that the fire was completely extinguished, although officials are working to contain a massive 30,000-pound propane tank that has a leaking valve.

Nearby media were told to move back Tuesday morning, but no new evacuations were ordered. Crews were dousing the tank — one of three massive tanks on the plant's property — with water, and a tanker was emptying the propane.

Tavares police Lt. Jason Paynter said that had one of the massive tanks exploded during in the previous night's fire, the results would have been "catastrophic."

Keith said, "There were some serious injuries, but it could have been a lot worse."

In the last three months there have been eight plant fires or explosions around the country including the fertilizer blast in West, Texas that killed 15. NBC's Mark Potter reports.

The fire chief, who lives less than 3 miles from the plant, said the explosion sounded "like a car hit our house."

“It shook my house, so I knew it was bad right off the bat,” he said.

Residents of the area told NBC station WESH of Orlando that flames from the explosions could be seen for several miles, but there were no reports of damage to the surrounding buildings.

"It sounds like bombs are going off," Norma Haygood, a nearby resident, told WESH.

No deaths were reported, Herrell said. Three male victims were in critical condition, Orlando Regional Medical Center told NBC News. Two were airlifted; a third was transported by ambulance.

Authorities initially declared a one-mile evacuation zone around the plant, but they later scaled that back to a half-mile.

"We feel that there is no longer any danger" to the area around the plant, Herrell said.

Twenty-four or 26 people were scheduled to work the night shift at the 33,000-acre facility, according to plant managers, Herrell said. Authorities initially said 15 people were unaccounted for, but Herrell later said the company's management said that it had accounted for all of the people it knew were in the plant at the time of the initial explosion.

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Some of them showed up at other locations, according to Blue Rhino, Herrell said.

The plant housed about 53,000 20-pound propane cylinders, Herrell said, the kind used in backyard barbecues.

"They store the propane cylinders on different parts of the property, and as the fire spread, there were more and more explosions," he said.

Explosions continued until 1 a.m. ET Tuesday, roughly 2½ hours after the first blasts were reported.

Don Ingram, a former plant production supervisor at the plant, said his son felt one of the explosions in their home 6 miles away.

Ingram told WESH that the back area of the plant was "lined with propane tanks stacked four or five high on plastic pallets."

"I don't think you fight this fire," he said. "It's just too dangerous."

Blue Rhino is a subsidiary of Ferrellgas Partners, the second-largest distributor of propane in the U.S.

Azhar Fateh of NBC News contributed to this report.

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