Workers who were inside a Tennessee explosives manufacturing plant at the time of a “devastating blast” on Friday are presumed to be dead, authorities announced on Saturday.

“I can tell you that more than 300 people have been through almost every square inch of this facility, and at this time, we’ve recovered no survivors,” Humphreys County Sheriff Chris Davis said during a press conference on Saturday.

Davis added, “We can assume that they are deceased at this time.”

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

Davis said the search has now transitioned 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 Bureau of Alcohol, Tobacco, Firearms and Explosives are also at the scene to help law enforcement.

Previously, officials stated that 18 people were unaccounted for after the blast, according to a statement from the Humphreys County Emergency Management Agency. On Saturday, officials did not provide a specific number of individuals they have recovered from the scene.

Authorities said they will 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.

Four to five people were brought to hospitals, according to the sheriff, who did not detail their injuries.

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.”

“This is not going to be something that we’re going to be like a car wreck or something like that, that we’re just going to clean up the debris and leave. We’re going to probably be here for a few days,” he said.

“We’re trying to take as much time as is needed right now. We’re prioritizing people that are involved, their families and trying to be very compassionate toward them,” he continued.