Texas State Fire Marshal Chris Conneally says the inquiry into the fire and explosions at the West, Texas, fertilizer plant remains an open case, with the cause "undetermined."
The cause of the deadly explosions at a Texas fertilizer plant last month remains undetermined, state and federal officials said Thursday.
Robert Champion, the agent in charge of the Dallas office of the Bureau of Alcohol, Tobacco, Firearms and Explosives, said at a briefing that investigators hadn't been able to rule out the possibility that the two blasts at West Fertilizer Co. were caused by an intentionally set fire.
The briefing was delayed a half-hour so authorities could talk to the families of the victims, said state Fire Marshal Chris Connealy, who promised to "leave no stone unturned to make sure everything is done."
On Thursday investigators said they still don't know what caused the initial fire, but they have ruled out smoking, weather and spontaneous combustion. NBC's Brian Williams reports.
"This community has suffered a great tragedy," he said, adding that 30 different local, state and federal agencies were working "with one common goal: to understand what happened so we can give closure to these families."
The explosions in the town of West, near Waco — which killed 15 people and injured hundreds of others on the night of April 17 — devastated a 37-square-block area, creating a crater 93 feet wide and 10 feet deep, Champion said.
Twelve of the dead were firefighters and other first responders, and Champion paid special tribute to them.
"They were doing their job and showing their bravery when they were fighting that fire," he said.
Investigators said the fire began in a fertilizer and seed building called the seed room. They said the possible causes included arson, a failure of one of the plant's two electrical systems and a compromised battery on a golf cart.
The golf cart had been recalled from the manufacturer, said Brian Hoback, a national response team investigator for the ATF, who said "there's a history of golf carts' actually starting fires" when their batteries fail. He said the cart couldn't yet be ruled out because it hadn't been fully recovered from the scene.
Many other triggers had been speculated upon as the cause, including the weather, some sort of spontaneous ignition, failure of the facility's second electrical system, two ammonium compounds used in the fertilizer-making process and smoking. Investigators said all of those had been ruled out.
And they chillingly said the explosions could have been much worse.
The fire caused at least 28 tons of ammonium nitrate, a highly combustible powder, to explode in the seed room, they said. Sitting outside was a rail car holding about 100 more tons of the compound — which fortunately didn't blow up.
Because the inquiry is being handled as a criminal matter, Champion and other investigators refused to go into other details of their investigation, which they said was expected to take several more months.
West Fertilizer said in a statement that it would have no comment other than that "the authorities repeatedly emphasized that their investigation continues, as does ours."
Champion, meanwhile, wouldn't comment on the arrest of Bryce Reed, a paramedic who helped the victims, who pleaded not guilty Wednesday to a count of unlawfully possessing an unregistered destructive device.
LM Otero / AP file
The explosion April 17 at West Fertilizer Co,. killed 15 people and injured hundreds more.
This story was originally published on Thu May 16, 2013 6:59 PM EDT