WEST — The cause of a fertilizer plant explosion here that killed 15 people on April 17 has been ruled “undetermined,” officials announced at a press conference in the town's high school parking lot on Thursday.
While an investigation into what triggered the blaze is ongoing, investigators’ examination of the scene has concluded. Because they cannot rule out an intentionally set fire, the matter is still considered a criminal investigation.
In addition to the possibility of a criminal act, Robert Champion, a special agent with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, said that other potential causes include the facility’s 120-volt electrical system and a potentially faulty golf cart. Investigators ruled out the possible rekindling of a previous fire, smoking, weather, the facility's 480-volt electrical system and the ammonium nitrate itself.
Officials told reporters at the press conference that there have been cases of battery-powered golf carts starting fires. A brake pad and an axle from a golf cart that was stored in the room where the fire began have been recovered, but there is not enough evidence to determine if it played a role.
A West paramedic named Bryce Reed was arrested last week and indicted for allegedly possessing materials that could be used for the construction of a pipe bomb. He has pleaded not guilty, and investigators on Thursday declined to comment on whether he had any connection to the blast at the fertilizer plant.
They also declined to speculate on whether or not the explosion or the fire that preceded it resulted from any regulatory failures.
Heat from a fire that was initially reported at 7:29 p.m. on April 17 led to two explosions at 7:51 p.m., investigators said, accounting for a total of 28 to 34 tons of ammonium nitrate. The force was equivalent to 15,000 to 20,000 pounds of TNT exploding.
The blast left a crater 93 feet wide and 10 feet deep, and homes and businesses were damaged as far as 37 blocks away from the plant. Of those killed in the blast, 12 were firefighters or other first responders. Texas State Fire Marshal Chris Connealy called the incident “one of the worst in history for first responders.”
In addition to the ammonium nitrate that exploded, another 20 to 30 tons housed at the plant did not explode. An additional 100 tons were stored in a nearby railcar that was destroyed in the blast, though it did not explode. Investigators said all of the ammonium nitrate was stored in wooden bins.
Texas Assistant State Fire Marshal Kelly Kistner said that more than 20,000 man hours have been spent on the investigation so far. Champion said that when the ATF is called to a crisis scene, its average stay is three to seven days. It has maintained a presence in West for more than 30, putting it on par with the 1995 Oklahoma City bombing.
“The tragedy in West has dramatically changed the lives of many in this tight-knit community, forever leaving its mark on the town and in the hearts of those who call West home,” Gov. Rick Perry said in a statement on Thursday. “While the cause of the fire remains undetermined and the investigation continues, this tragedy has shown the world the definition of compassion, from volunteer firefighters across the state rushing to help their colleagues at the scene to friends, neighbors and Texans stepping in to help those who lost so much in the blast.”
More information is expected as the investigation continues, though officials were unable to say if they would be able to whittle down the list of three potential causes any further. The State Fire Marshal’s Office is also conducting a line-of-duty investigation into the first responders who lost their lives. Kistner said it would take several months for that report to be finalized.