The fire started in a freezer section of the Cargill Meat Solutions plant in this western Arkansas town of 4,000 residents, said Logan County emergency manager Don Fairbanks.

Workers "were doing some welding on some fans," Fairbanks said. "The welders had put their equipment up and turned around and there was a fire."

Authorities said dispatchers received the first emergency call about the fire at about 1 p.m. Sunday, and at least one fire could still be seen burning Sunday night.

"The entire facility is gone," said Tonya Roberts, a spokeswoman for the emergency response effort.

The Cargill Inc.-owned plant, which employs about 800 people and produces more than 2 million pounds of ground beef and steak per week, is the town's largest employer, according to the Booneville Chamber of Commerce.

Lori Hayes, a human resources manager for the plant, said corporate officials would come to the plant in the coming days to assess the damage. She said it was too early to say whether the plant would be rebuilt.

"We are asking all employees not to show up tomorrow," Hayes said.

Mark Klein, a spokesman for Minneapolis-based Cargill Inc., said the plant is closed Sundays but that about 20 contractors and a few other employees were at the site at the time of the fire.

"Everybody's good. There's been no injuries," said Gina Kinney, a dispatcher with the Logan County Sheriff's Department.

The fire involved an estimated 88,000 pounds of anhydrous ammonia, plus the plant had 100,000 pounds of nonflammable carbon dioxide, which is used in refrigeration systems, she said.

Firefighters were unable to fight the blaze using conventional equipment because of the danger from the gasses, so they opted to let it burn itself out.

Authorities said that as the fire grew, a series of small explosions rattled the 150,000-square-foot plant, which consists of metal-framed buildings. By late Sunday afternoon, a hazardous materials team entered the smoldering plant to check the gauges on the anhydrous ammonia tanks. They all read empty, said Roberts.

"It either went up into the atmosphere or burned up," Roberts said at a news conference. "The piping from the tanks runs all throughout the plant, so there are lots of places for it to leak or burn."

Cargill officials did not offer a damage estimate, but Logan County Judge Edgar Holt estimated the plant was worth more than $100 million before the fire.

"They just did a $40 million expansion and it's gone," Holt said.

Police began evacuating homes shortly after the fire was reported.

Cody Moore, an emergency coordinator at Booneville Community Hospital, said the facility's 12 patients were sent to a hospital in Waldron after the evacuation order. He said 50 staffers stood ready to care for any victims.

Nine nursing home residents were among those told to leave the area. They were taken to a nursing home in nearby Greenwood. It was unclear when residents might be allowed to return to their homes.

Meredith Voges, 22, said she heard the explosion while staying at a hotel near the plant.

"The whole factory was ablaze with black smoke flying into the air, plumes of smoke," said Voges, who called the scene chaotic.

Cargill Inc. has about 2,000 employees in Arkansas, according to its Web site.