An explosion at a Tennessee military munitions plant left multiple people dead and missing on Friday, authorities said, as secondary blasts forced rescuers to keep their distance from the burning field of debris.

The blast, which people reported hearing and feeling kilometres away, occurred at Accurate Energetic Systems in rural Tennessee.

The company’s website says it makes and tests explosives at an eight-building facility that sprawls across wooded hills in the Bucksnort area, about 97km (60 miles) southwest of Nashville.

“We do have several people at this time unaccounted for. We are trying to be mindful of families and that situation,” Humphreys County Sheriff Chris Davis said at a news conference. “We do have some that are deceased.”

The cause of the explosion, which Davis called “devastating”, was not immediately known, and the investigation could take days, the sheriff said.

Aerial footage of the aftermath by WTVF-TV showed the explosion had apparently obliterated one of the facility’s hilltop buildings, leaving only smouldering wreckage and the burnt-out shells of vehicles.