No hope of survivors in US munitions factory blast

Investigators now believe a massive blast at a Tennessee military explosives facility killed 16 people.

Officials had previously said 18 people were unaccounted for in Friday's explosion, but two people whose vehicles and personal items were found at the scene were not actually there when the blast erupted, Humphreys County Sheriff Chris Davis said at a press conference on Saturday.

The explosion, which was felt for kilometres, levelled a building at the five square kilometre headquarters of Accurate Energetic Systems in Bucksnort, about an hour's drive west of Nashville. Officials have notified the families of all 16 people killed, the sheriff said.

"We'll call them victims, our loved ones," a tearful Davis said.

Earlier on Saturday, Davis confirmed the operation had shifted from rescue to recovery and that investigators would use DNA testing to confirm the identities of those who died.

Investigators, including agents from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives, were still working to determine the cause of the explosion, officials said.

The presence of explosives and other ordnance at the property has made searching the scene complicated.

In a statement on Friday, the company thanked first responders but did not indicate a possible cause.

"Our thoughts and prayers are with the families, coworkers, and community members affected by this incident," the company said.

Accurate Energetic Systems develops, manufactures, and stores explosives for "military, aerospace, and commercial demolition markets," according to the company's website.

The headquarters includes eight production buildings and a quality lab.

A small ammunition explosion at the plant in 2014 killed one person and injured three, according to local news reports.