At Least 8 Injured After 'Humongous' Blasts at Florida Propane Plant

July 30, 2013— -- At least eight employees, four of them critically, were injured after several large propane tanks exploded late Monday night at a gas plant in Tavares, Fla., officials said, sending "humongous" flames and smoke into the sky.

The tanks at the Blue Rhino gas plant, which is about 40 miles northwest of Orlando, began exploding around 11 p.m. Monday. Authorities initially reported that 15 people were unaccounted for, but later said that they were found, according to Lake County Sheriff's Office Lt. John Herrell, who addressed reporters in an early-morning news conference.

There have been no reports of fatalities. The Blue Rhino plant refills propane tanks typically used for barbecues and other activities.

"People from very far away and in towns six, seven, eight, 10 miles from here were reporting feeling their homes shaking," Herrell said.

WATCH: Large Explosions Rock Florida Propane Plant

Tavares Fire Chief Richard Keith said officials believe the explosion was an accident and caused by human error.

The Orlando Regional Medical Center said it received three male patients who were listed in critical condition and being treated for burns. Shands Hospital said it was treating one person in critical condition.

Fire officials said 24 to 26 people were scheduled to work at the gas plant when the explosions and fire broke out. Blue Rhino executives told ABC News that all scheduled employees have been accounted for and are alive.

Lt. Herrell said the workers who escaped the plant were toward the front of the property, which is separate from where the explosions took place.

Ashley McCormick lives in neighboring Mount Dora, Fla., and told ABC News by phone that she could see the fire from 7 miles away.

"You could definitely see the fire from across the lake. It was humongous even from seven miles away," McCormick said. "You could hear the explosions, just one after another and then after it would explode, a fireball would shoot up into the sky."

There were 53,000, 20-pound cylinders at the gas plant where the explosions took place, officials said.

"I have heard tons of booms for at least 30 minutes," Mount Dora resident Blake Cottle told ABC News affiliate WFTV-TV.

Officials said roughly 50 homes in the area were evacuated. Herrell said an evacuation zone was initially a one-mile radius but had been reduced to a half-mile radius. First United Methodist Church in Tavares has opened its doors to take in families.

There is no information to suggest the public should be concerned about the propane in the air, Herrell said.

Authorities say they are not aware of any damage to other properties, but will get a better look at the surrounding area later this morning. Police were checking on reports of projectiles from the fire damaging a local strip mall.

ABC News' Rebecca Lee and Scott Withers contributed to this report.