The Morning News broke the news this morning that officials had narrowed the cause of last month's deadly West, Texas fertilizer plant explosion to one of three things: a golf cart, an electrical short, or criminal activity. That wasn't terribly narrow, but there was a press conference scheduled this afternoon, so we thought investigators might be more specific.
"The cause of this fire is undetermined," State Fire Marshal Chris Connealy told reporters, explaining that fire investigators make that ruling when a "cause cannot be proven to an acceptable level of certainty because of insufficient information or when multiple causes can't be eliminated."
Several causes have been ruled out. The fire wasn't caused by a rekindle as had been speculated, because there was no earlier fire. It also wasn't spontaneous, nor was it caused by the 480-volt electrical system.
That leaves the complex's 120-volt electrical system, a golf cart, or arson.
Investigators with the State Fire Marshal's office and Bureau of Alcohol, Tobacco, and Firearms pointedly declined to speculate on the latter or the potential role of former EMT Bryce Reed, charged with possessing a pipe bomb, saying the criminal investigation is ongoing.
They were more forthcoming about the golf cart. "There is a history of golf carts starting fires," ATF investigator Robert Champion said, explaining that their batteries store a good deal of charge and have been known to malfunction. So far, they've only found the vehicle's brake pad and axle. "We don't have enough pieces of the golf cart nor do we have enough pieces of the building that would have been around the golf cart to eliminate that."
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However the fire started, the explosion happened not long after. Firefighters were called to the fire at 7:29 p.m. and arrived nine minutes later. By 7:51 p.m., the heat from the fire had caused the ammonium nitrate, stacked in wooden crates in the seed building, to change states and become unstable. It was the shock from falling machinery that triggered the first explosion, which triggered a second explosion millliseconds later.
The ammonium nitrate that exploded was only a fraction of what blast carried the force of 15,000-20,000 tons of TNT. The damage extended a half mile. Evidence was discovered as far as two-and-a-half miles away. The resulting crater measured 10 feet deep by 93 feet wide.
It was there that investigators focused their efforts, excavating the area much like archaeologists would. They reconstructed the seed building and its electrical systems as best they could, then moved outward. During the course of their investigation, they sifted through ton upon ton of corn and milo kept in nearby silos.
There was also forensic mapping, chemical analysis, forensic audits, aerial photography, computer modeling, and other efforts that cost the ATF well more than $1 million. And that number is only going to increase as the investigation continues.