Federal investigators said they pinpointed the source of a deadly explosion that killed 15 people, injured dozens more, and destroyed homes in the central Texas town of West.
Agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives said they determined a stockpile of ammonium nitrate detonated on April 17 at the West Fertilizer company.
However, ATF Special Agent Franceska Perot cautioned that while investigators believe ammonium nitrate is what exploded, they still do not know the source or cause of the fire that preceded the explosion or exactly what triggered the explosion.
Ammonium nitrate is a potentially explosive chemical typically found at fertilizer plants, but fire alone cannot cause this chemical to explode.
Investigators are now trying to determine what other contributing factors may have led to the explosion.
Investigators said they have ruled out weather, natural causes or the tanks of anhydrous ammonia on the property as the cause of the initial fire.
While investigator have not yet pinpointed the source of the initial fire they said they have determined it did not start in the bin of ammonium nitrate stored in a building on the property.
Local 2 Investigates reported that state records showed the company reported handling tons of ammonium nitrate each year as part of its operation.
State and federal investigators said to date they have developed over 200 leads and conducted over 400 interviews as part of the investigation into the explosion.