TAVARES, Fla. — Equipment malfunction and human error are among the possible causes of a series of explosions that spawned a 20-by-20 foot fireball at a central Florida propane plant and left eight injured, authorities said.

Tavares Fire Chief Richard Keith identified the possible causes Tuesday, but said sabotage was not suspected.

The federal Occupational Safety and Health Administration launched an investigation into the Monday night incident at the Blue Rhino propane plant, as did the Florida State Fire Marshal’s office.

No one died, but eight workers were injured, four critically, including one worker who was hit by a car on a nearby road while fleeing the explosions. Officials said the damage could have been significantly worse if three 30,000-pound propane storage containers had caught fire at the plant that refills propane tanks for gas grills and other home uses. About 50 nearby houses were temporarily evacuated, though none was ultimately damaged.

If the large tanks had exploded, “it would have wiped us out,” said Lake County Battalion Chief Chris Croughwell.

After hearing two explosions, maintenance worker Gene Williams looked outside to see the fireball rising.

Moments later, a forklift worker stumbled into the building. His legs and face were burned. Exploding 20-pound canisters of propane began raining down around them.

Bright orange flames would grow as high as 200 feet, fueled by the exploding canisters that shot through the air like fireworks. Houses nearby shook, and residents awakened to the sound of “boom after boom after boom.”

Williams said it appeared to begin about 100 yards from the loading dock in an area where some of the plant’s 53,000 20-pound propane canisters are stored on plastic pallets.

The plant’s two-dozen workers were preparing to go home when the explosions started, said Williams, who works the third shift.