“This means this fire was a criminal act," ATF Special Agent in Charge Rob Elder said at a news conference.
Federal and local officials announced the findings at the conference Friday. No arrests have been made in the case. ATF announced a reward of $50,000 for information leading to the arrest of anyone responsible for the fire, which led to the explosion.
The blast, which killed 15 and injured more than 260, happened at 7:51 pm, some 20 minutes after signs of a fire were reported to the local 911 dispatch center. Several local fire departments responded to the blaze. A dozen emergency responders were killed when the when fertilizer at the facility exploded.
The site stored between 40 and 60 tons of the ammonium nitrate fertilizer. In comparison, an estimated 4,800 pounds of that same chemical fertilizer was used to construct the truck bomb which destroyed the Alfred P. Murrah Federal Building in 1995.
The explosion left a crater nearly 93 feet wide and 12 feet deep. Material from the plant was found more than two and a half miles away.
The insurance-related losses from the blast were estimated to be around $230 million dollars, according to a report on the incident by the U.S. Chemical Safety and Hazard Investigation Board.