A 2013 fire that caused a massive explosion at a fertilizer plant in Texas, killing 15 people, was intentionally set, authorities said Wednesday.
There is now a $50,000 reward for information leading to the arrest of the person or persons responsible for setting the blaze at the West Fertilizer Plant in the small town of West, the Bureau of Alcohol, Tobacco, Firearms and Explosives said in a statement.
The April 17, 2013 blast also injured 300 people, destroyed more than 500 homes and left a crater 93 feet (28 meters) wide and 12 feet (3.7 meters) deep.
The explosion was so powerful that it registered as a 2.1-magnitude earthquake.
Of the 15 people killed, 12 were first responders.
The fire was deemed "incendiary," or intentionally set, after "all viable accidental and natural fire scenarios were hypothesized, tested, and eliminated," the ATF said.
Investigators determined that between 28 and 34 tons of ammonium nitrate exploded in two blasts which were just milliseconds apart and caused by the heat of the fire and the impact of falling debris.