The fire and explosion at the West, Texas, fertilizer plant is still under investigation and the cause of the fire that ignited an ammonium nitrate explosion is undetermined at this time.
That was the announcement by the Texas fire marshal's office and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) at a news conference May 16 at the site of the explosion that resulted in the death of 15 people.
The spokespersons explained that the excavation and investigation of the site has been completed with one piece of material thrown from the explosion found 2.5 miles away. The majority of the evidence was gathered within about a one-half mile radius.
Kelly Kistner, assistant state fire marshal, said, "The origin of the fire has been determined to be in the fertilizer and seed building, in the northern area that was referred to as the seed room."
The investigators determined that the seed storage room had a wooden wall separating it from the ammonium nitrate that exploded, and there were two explosions milliseconds apart, which would have appeared and heard as one massive explosion.
Kistner disclosed that the investigation has determined between 28 and 34 tons of ammonium nitrate exploded (the equivalent of an explosion from 15,000 to 20,000 pounds of TNT), 20 to 30 additional tons of ammonium nitrate in storage did not explode and an additional 100 tons in a rail car also did not explode.
That total amount of ammonium nitrate on the site was tallied to be approximately 150 tons, which was mentioned as being under the amount reported to the Department of Homeland Security by the fertilizer plant ownership; 270 tons maximum amount to be stored was reported on the company's Tier 2 report for establishing tier security requirements, noted Kistner.
The investigators are refusing to provide any other comments about regulatory requirements, or related issues at this time, claiming that "the investigation is open and ongoing." The only aspect of the investigation completed is the excavation and site evidence gathering.
"An undetermined cause..occurs when the cause cannot be proven to an acceptable level of certainty or there is insufficient information or if multiple causes cannot be eliminated.The causes that have not been eliminated are the 120-volt electrical system in the building, a golf cart and an intentionally set fire," said Kistner.
The fire and explosion could have been classified as naturally caused, an accident, incendiary devise caused or undetermined. The investigators have basically left the cause open as undetermined while state and federal law enforcement, including AFT, continue the investigation.
It is logical to look at the electrical system for sparking the fire, and battery operated golf carts have been linked to previous fires; therefore, it continues to be looked at as the potential ignitor. But determining much about the golf carts potential involvement is extremely difficult because only two pieces of the golf cart have been identified, the biggest being an axle and the other a brake pedal pad, it was explained at the press conference.
Because there is an ongoing criminal investigation centered around a paramedic who possessed materials for making a pipe bomb, the officials at the May 16 media conference would not accept questions about persons or criminal acts possibly causing the fire.