A blast in rural Tennessee that levelled an explosives plant and was felt for miles around killed 16 people and left no survivors, state authorities said.

"We can assume that they are deceased at this time," Humphreys County Sheriff Chris Davis told a news conference on Saturday.

The factory owned by Accurate Energetic Systems made explosives for both military and demolition purposes.

The explosion destroyed an entire building at the plant's large campus, shook homes miles away and sent debris flying, local media reported.

Davis said DNA testing will be used to identify remains.

"But we're going to have to slow walk that because of the scene, the way that the scene is," Davis said.

He said staff from several federal agencies including the FBI have been sent to the blast site to help with the investigation. (Agencies)