16 people dead after Tennessee explosion

What he's saying: Humphreys County Sheriff Chris Davis told reporters it was "the most devastating scene that I've seen in my career." The blast completely leveled the building.

• "There's nothing to describe," he said at a press conference. "It's gone."

The FBI and ATF are on the scene during the investigation, along with law enforcement from across the state, including Nashville's bomb squad.

• The Tennessee Emergency Management Agency said there does not appear to be any ongoing threat to the area.

Editor's note: This story was updated to reflect official reports on the number of deaths tied to the explosion.