June 9 (Bloomberg) -- A roof collapse at a ConAgra Foods Inc. plant has injured 32 workers and left three others missing, the company said.

An explosion at the factory in Garner, North Carolina, which makes Slim Jim meat snacks, caused extensive damage to the roof, Garner Police Sergeant Joe Binns said today in an interview. No deaths have been reported and hazardous-material teams were on the scene, Binns said.

Search-and-rescue teams were looking for the missing workers hours after the 11:30 a.m. incident, about seven miles from Raleigh, Teresa Paulsen, a spokeswoman for ConAgra, said in a telephone interview. Officials previously said only two people were still missing.

“We don’t have any information conclusively on the cause, we don’t want to speculate,” Paulsen said of the explosion and collapse.

The U.S. Chemical Safety Board, a Washington-based agency charged with investigating industrial chemical accidents, has sent a team to the site, it said in an e-mailed statement. The board makes safety recommendations to plants, industry organizations, labor groups and regulatory agencies and doesn’t have authority to issue citations or levy fines, it said.

Hillary Cohen, a spokeswoman for the agency, said she doesn’t know how long the investigation will take or when a report will be ready.

Burn Victims

At least four of the injured were being treated for burns covering 40 percent to 50 percent of their bodies, said Bruce Cairns, medical director of the North Carolina Jaycee Burn Center at the UNC Medical Center. He said other seriously burned patients may still be admitted to the center.

About 300 employees were in the factory at the time of the explosion, Paulsen said.

Binns said rescuers have identified areas in the collapsed portion of the building where people may be trapped. Crews have been unable to search those areas because a severe thunderstorm forced them to halt operations this afternoon, he said. Rescuers used cameras to search some cars damaged in the collapse, according to Binns.

Starting at 8 p.m. two teams of 24 rescuers will work on the search in 12-hour shifts, Binns said.

The plant employs about 900 workers in three shifts and runs 24 hours a day, seven days a week, Jeff Mochal, a ConAgra spokesman, said in a telephone interview. The factory handles all of ConAgra’s Slim Jim production, Paulsen said.

Fire Extinguished

Emergency workers put out a fire on the south side of the plant after the explosion, Binns said. Ammonia used for refrigeration at the plant doesn’t pose a danger, he said.

ConAgra, which also makes Orville Redenbacher’s popcorn and Chef Boyardee canned pasta, fell 16 cents to $19.60 at 4:15 p.m. in New York Stock Exchange composite trading. The shares climbed 20 percent this year before today.

Executives and safety officials from the Omaha, Nebraska- based company headed to the 50,000-square-foot plant on a corporate jet, Mochal said. The company bought the building at 4851 Jones Sausage Road in 1998.

To contact the reporters on this story: Duane Stanford in Atlanta at dstanford2@bloomberg.net; Brian K. Sullivan in Boston at bsullivan10@bloomberg.net.

Last Updated: June 9, 2009 18:42 EDT