Fire departments from across the Birmingham area responded to a gas line explosion in Shelby County that killed one person and severely injured several people Monday afternoon.

Earlier reports indicated that seven had been severely burned and many of them transported to UAB.

However, at 10:45 p.m., pipeline operator Colonial reported that five were injured and one fatality was discovered at the scene of the accident. Pipeline operator Colonial said the contractors "experienced an incident when the trackhoe it was using hit the line".

With a severe drought caused by weeks without rain, much of central Alabama has been plagued by multiple wildfires, forcing crews to try and keep the blaze from spreading across the landscape.

Coleen Vansant, a spokeswoman with the Alabama Forestry Commission, said crews were attempting to build a 75-foot-long earthen dam to contain burning fuel, which will be allowed to burn itself out.

Two wildfires caused by the explosion burned 31 acres of land, she said.

Homes around the blast scene were evacuated, and Capt. Jeff Hartley of the Shelby County Sheriff's Office said it wasn't clear when people might be able to return home.

"There's a large plume of smoke; there's a large fire. We're not sure exactly how it started or what caused it," he said.

Eight or nine subcontractors were working on the Colonial gas pipeline when it exploded around 3 p.m., Shelby County sheriff's Maj. Ken Burchfield confirmed. Colonial has now shut down both pipelines running through the area.

"The fire will not be out any time soon," Burchfield added.

Shelby County Sheriff John Samaniego said the Colonial subcontractors were trying to flush one of the lines. As they began to dig, that is when the explosion happened.

In addition to the injured victims, Samaniego said there's a possibility that two workers are still missing. The heat from the blaze, he said, is hindering the search for them.

The sheriff said the flames are still reaching about 50 feet in the air.

The explosion was in the 300 block of Grey Hill Road in the area of River Road and Highway 13. Firefighters from the Bessemer, Birmingham, Indian Ford and McAdory departments are assisting.

There are only two homes nearby - both are roughly a half mile from the explosion site. Those residents have been evacuated but because the area is so rural, Samaniego said he doesn't expect further evacuations.

Colonial has now shut down both pipelines running through the area. This explosion is about five miles west from a recent Colonial Pipeline gasoline leak.

The Georgia-based company said in a brief statement Monday evening that its top priorities are the health and safety of its work crews at the scene and protecting the public.

"Our deepest condolences go out tonight to the family and friends of the person who was lost today, and our thoughts and prayers are with those who were injured."

Flights in the area have been restricted, Gregory Robinson of the state emergency management agency announced Monday night. Only relief aircraft are authorized in the airspace.

Mason Chatman said he and a friend -- who recently purchased property near the site of the explosion -- were worried when they saw a black plume of smoke while driving on Interstate 65.

The two drove to the property, where Chatman's friend plans to build a house, fearing it might be threatened by the fire.

"He was afraid it was a lot closer than where it actually was," Chatman said. "Luckily, nothing has happened here."

Shelby County EMA officials are on the scene along with Shelby County sheriff deputies and pipeline officials. Roadways in the area will remain closed to all but local traffic to allow emergency personnel easy access.

"Typically we don't see external damage to a pipeline from ground-level activity, whether it's human or weather-related, except for some third party striking the pipeline with a piece of excavation equipment," Brigham McCown, former administrator of the federal Pipeline and Hazardous Materials Safety Administration told AL.com last month.

"That's now the leading cause of pipeline spills and accidents."

Gov. Robert Bentley said in a brief statement that his office is monitoring the situation and said his office is receiving updates from state and local authorities.

"Pray for workers, rescue personnel," Bentley said in the statement.

This is a developing story and will be updated.

AL.com reporters Dennis Pillion, Starr Dunigan, Connor Sheets and The Associated Press contributed to this report.