4:46: Chris Connealy , Texas State Fire Marshal, says after one of the most intense explosion investigations ever undertaken by the ATF, the cause of the fire and explosion in West on April 17, is officially undetermined, and the investigation continues.
Officials are still looking at possible causes that could have started the fire and the explosion, including the 120 volt plant, a nearby golf cart, and the possibility the blast might have been caused intentionally. The investigation is being treated as a criminal investigation, and again, it is ongoing.
UPDATE 5:26 PM - Here is more from the press conference: Fire Marshal Conneally said before the press conference, officials talked first to families impacted by the West, Texas tragedy. “We thought it was important to give them some aspects of closure, of explaining what happened. The community has suffered a great tragedy.”
He said the scene investigation is completed, even though the cause investigation continues. Conneally said investigators were going to "leave no stone unturned to make sure the fire’s cause was investigated."
He explained how fires and investigations are investigated. There are four classifications: Natural (lightning, for example), accidental, incendiary and undetermined.
An undetermined cause is found when a cause “cannot be proven to an acceptable level of certainty, or when multiple causes cannot be eliminated.”
Here are some details of the fire investigation and blast that killed 15, including 12 first responders.
On April 17, 2013, a fire was reported 7:29 pm at the West Fertilizer plant. At 7:51 pm, two explosions occurred.
Robert Champion, Special Agent in Charge, out of the Dallas ATF office, offered heartfelt condolences to West families who suffered the loss of loved ones, and thanked all involved in the investigation. Champion said his team has responded to 732 "call outs" – investigations – over the last 30 years, and this event was one of the longest "call outs" ever by an ATF team. He said it ranks with the Oklahoma City bombing, the first World Trade Center bombing (1993),the Pentagon fire on 9-11, and the East Texas truck fires three years ago. He said as for length of time, the average investigation lasts three to seven days. This one lasted thirty.
UPDATE: 5:33 pm. Champion explained possible causes that were investigated, and eliminated. For example, rekindling was eliminated because he said there wasn’t a fire at the plant that day. Spontaneous ignition was eliminated after looking into the 480 volt electrical system that ran heavy equipment in the plant. He said they also looked into anhydrous ammonia, ammonia nitrate, smoking, and weather. All were also eliminated as possible causes.
UPDATE 5:40 pm - As for ex-fire fighter Bryce Reed, arrested May 9 on federal charges of possessing a destructive device, Champion said authorities would not speculate whether possession of an unregistered destructive device had any connection to the West Fertilizer plant explosion.
And he reiterated the remainder of the investigation continues, to find a cause of the fire and explosion.