Updated

An explosion and fire destroyed a coffee shop Friday in a rural south Georgia city, seriously injuring three people, officials said.

The blast rocked tiny Homerville, a city of about 2,500 people, shortly after noon, prompting a warning from city officials for residents to avoid the downtown area.

Investigators determined a construction crew installing fiber optic cable had ruptured an underground gas line, causing natural gas to leak into a sewer line connected to the coffee shop, said Glenn Allen, spokesman for Georgia Insurance and Safety Fire Commissioner Ralph Hudgens.

"Inside the shop gas built up in the kitchen area and there was a spark, resulting in the explosion," Allen said late Friday.

Two employees and a customer were the only people inside the coffee shop when it exploded, Allen said. They were airlifted to a hospital in Gainesville, Fla., with "burns and other serious injuries," he said.

Investigators initially reported all three of the injured worked at the shop, Allen said, but later learned they were mistaken.

Allen said the explosion and a resulting fire destroyed the small, single-story building that housed Coffee Corner.

A photo taken by an investigator at the scene showed the building's roof had partially collapsed.

Brick walls were blasted apart, with bricks scattered in the parking lot and piled atop two cars parked beside the shop.

Homerville is roughly 30 miles from the Georgia-Florida line.

Officials used the city's Facebook page to urge residents Friday to stay away, referring only to "issues within the downtown area."

"First responders and all other crews need the area to be as free of traffic as possible in order to get their jobs done," the city's Facebook post said.

Nan Mikell, Homerville's city manager, did not immediately return phone and email messages.

No one answered the phone at the Clinch County Emergency Management Agency. The phone number for Homerville police was forwarded to Mikell's voicemail.

Homerville is about a four-hour drive southeast of Atlanta.

The Associated Press contributed to this report.