McARTHUR, Ohio (AP) — At least eight workers were injured Tuesday in a blast at an explosives manufacturing plant in southeast Ohio.

The explosion occurred about 10:30 a.m. at Austin Powder Co.'s Red Diamond plant near McArthur. It happened in a building where workers make detonating cord used in commercial blasting, said Mike Gleason, executive vice president.

Vinton County Sheriff Dave Hickey said employee Marletta Betts had burns over most of her body. She and co-workers Becky Castor and Debbie Hagerty were flown by medical helicopter to Ohio State University Medical Center. A fourth woman, Helen Hall, was taken to a local hospital, Hickey said. All four women are from McArthur. Their conditions and ages were not available.

Other injured people were treated at the scene.

The cause of the explosion was under investigation, but Hickey said there was no reason to believe criminal activity was involved.

Cleveland-based Austin Powder manufactures explosives for the mining and construction industries and performs blasting services. About 200 people work at the McArthur facility, which was built in the 1930s and includes dozens of buildings.

The cord the women were manufacturing contains a small amount of high explosive, said Kim Riddell, spokeswoman for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

Investigators have not entered the building as they await an assessment on its safety, Riddell said. The building sustained its heaviest damage to the roof, she said.

ATF, the federal Occupational Safety and Health Administration and the State Fire Marshal's office were investigating with local authorities.