Although homes have been rebuilt and a new high school is up and running, the town of West, Texas hasn’t been able to close the terrible chapter of its history that began on April 17, 2013 – the day that an explosion at the West Fertilizer company killed 15 people and leveled dozens of buildings.

After announcing a year ago that the fire that began the tragedy was intentionally set, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) has made no arrests in the case. A spokesman at the time said all possible causes, both accidental and natural, were investigated before investigators reached that conclusion.

The U.S. Chemical Safety Board (CSB) also found that the way the company stored the ammonium nitrate that exploded and its failure to develop a plan with local emergency responders contributed to the severity of the incident (most of those who died were firefighters).

In addition to the fatalities, 200 people were injured and more than 500 homes destroyed in a 37-square-block area by the blast, which left a 12 foot deep crater in its wake.

News sources reported that the investigation into the blast cost an estimated $2 million. The ATF is offering a reward of up to $50,000 for information that leads to the arrest and prosecution of the person or people responsible for the explosion and fire.