A "devastating" blast at a Tennessee explosives manufacturing plant on Friday is believed to have left 16 people dead, authorities announced on Saturday.

At a press conference on Saturday, Humphreys County Sheriff Chris Davis said authorities had narrowed down the number of workers missing after the massive blast to 16.

"At this time we have not located any survivors, and we are making the assumption that all are deceased at this time," Davis said.

The explosion occurred Friday morning at Accurate Energetic Systems in McEwen, located about 50 miles west of Nashville.

Earlier, authorities had said 18 people remained unaccounted for after the blast. However, the sheriff said Saturday evening that two people, whose vehicles and belongings were found at the scene, were later determined not to be on site at the time of the explosion.

The cause of the explosion has not yet been determined, according to officials with the Bureau of Alcohol, Tobacco, Firearms and Explosives and the National Center for Explosives Training and Research.

At a briefing earlier Saturday, Davis said the search had transitioned from a search and rescue into a recovery effort.

"It's a great loss to our communities," Davis said while holding back tears. "We are dealing with explosions, and I would say at this time, we're dealing with remains."

Davis said officials are now in the process of identifying the remains and are using cellphone data to determine whose devices were at the site at the time of the blast.

"As we get into this, we find it more devastating that we thought initially," he said.

Davis emphasized that the investigation is a "slow, methodical" process due to the nature of the scene and the volatility of the chemicals currently present.

Certified explosive specialists and bomb technicians with the ATF were also at the scene to help law enforcement.

Authorities said they would be conducting some controlled explosions throughout the day on Saturday to clear out the dangerous materials currently at the scene, so they can safely continue the investigation and recovery efforts.

Asked to describe the building where the explosion occurred, Davis said, "There's nothing to describe. It's gone. It's probably been one of the most devastating situations that I've been on in my career."

The sheriff said during an earlier briefing that this is a "very big investigation."