A 2013 Texas fertilizer plant explosion that wounded 200 and killed 15 — including 12 first responders — was caused by an act of arson, investigators announced Wednesday. The State Fire Marshals deemed the April 2013 fire a "criminal act" and said it was intentional. No arrests have been made, although officials said they were on "the right track." Authorities ruled the fire was deliberate after conducting more than 400 interviews. The night of the explosion, a fire had broken out at the West Fertilizer Co.