COOK COUNTY — Arson is the cause of a fire that destroyed the renowned Catfish House just over the Cook County line off Adel Highway Thursday night, authorities said Friday.

The Georgia Fire Marshal’s Office issued a press release Friday, stating that Cook County Sheriff Charles W. Bryant, the Georgia Bureau of Investigation and John W. Oxendine, Georgia’s insurance and safety fire commissioner, are investigating the fire.

The blaze occurred about 10:24 p.m., after all employees had left. No one was inside the building at the time, the fire marshal’s office said.

The entire building, about 11,200 square feet, was destroyed, and the remains were still smoldering at sundown Friday. Only a concrete room at the rear of the restaurant remained standing. A propane gas tank nearby, which was reportedly full, did not explode.

The loss was estimated at $850,000.

Employees who were working Thursday night said the last customers came in about 9 p.m. and had left by 9:30 p.m. Steven Carter, 18, a cook and busboy at the Catfish House, said he left with other employees about 10:15 p.m.

“I made sure that all the fire was out,” he said, referring to the grills and fryers. “Everything was normal.”

Employees said the owner, Peggy Parr, and her daughter-in-law, Jennifer Barnes, were still inside when they left.

Parr and Barnes could not be reached for comment.

Karen McGowan, who has lived next door to the restaurant for three years, said she saw flames coming out of the building shortly before 10:30 p.m. and heard explosions inside the building that ignited the entire structure.

“I came in after dark and I was busy cooking, so I really wasn’t paying attention like I usually do,” she said. “After the explosions, I saw flames shoot up and embers were going everywhere.”

Another owner opened a restaurant there in 1982 under the name “The Little River Barbecue and Fish.” Since then, it has gone through at least one other owner before Parr bought it last year, employees and neighbors said. Under Parr’s management, business had slowed noticeably, they said.

“There used to be cars parked everywhere,” McGowan said pointing to a grass lot in front of her house. “It’s slowed tremendously.”

However, Holie McDonald and his family drove up from Jasper, Fla., Friday afternoon expecting to eat at the restaurant.

“I thought (the food) was great,” he said. “I can’t believe that it’s gone.”

Commissioner Oxendine asks that anybody with information about this fire please call the Georgia Arson Hotline at 1-800-282-5804. Rewards of up to $10,000 are given for information leading to the arrest and conviction of an arsonist, an Oxendine spokesman said. Calls are taken 24 hours a day, seven days a week; callers may remain anonymous.

First-degree arson carries a penalty of up to 20 years in prison and a fine of up to $50,000.