Investigators with the Bureau of Alcohol, Tobacco, Firearms and Explosives announced Saturday that this week's fatal explosion at a middle Tennessee ammunition factory has been ruled accidental.

Our Nashville NBC affiliate WSMV-TV reports, the ATF deemed the incident as non-criminal in nature and classified it as an industrial accidental explosion.

Preliminary findings showed the explosion occurred in the area of the factory's mezzanine that fed the loading machine that resulted in the death of one employee and sent three others to the hospital.

The ATF National Response Team investigation the Rio Ammunition manufacturing plant alongside agents with the agency's Nashville Field Office and the Tennessee Bomb and Arson Section.

The Rio Ammunition facility was deemed safe to enter Friday, and crews began clearing debris.

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