By Lisa Maria Garza
WEST, Texas (Reuters) - Investigators are expected to announce on Thursday the results of a probe into what caused last month's fertilizer plant explosion in West, Texas, that killed 14 people and obliterated sections of the small town.
The State Fire Marshal's Office and the Bureau of Alcohol, Tobacco, Firearms and Explosives are scheduled to release the findings of their joint investigation at an afternoon news conference.
Texas officials on Friday announced a criminal investigation into the blast.
Investigators confirmed last week that ammonium nitrate stored at the West Fertilizer Co detonated in the April 17 explosion. The fire and subsequent blast at the facility also injured around 200 people.
More than 70 investigators have developed more than 200 leads, from which more than 400 interviews have been conducted, investigators said last week.
Investigators believe the fire started somewhere in the 12,000-square-foot (1,100-square-meter) fertilizer and seed building.
So far, investigators have ruled out possible causes including the weather, natural causes, a fire within the ammonium nitrate bin, a railcar containing ammonium nitrate and anhydrous ammonia -- another fertilizer component.
Additionally, they said water used during fire-fighting activities did not contribute to the cause of the explosion as some had speculated.
Bryce Reed, a paramedic who was among the first responders at the explosion site, was arrested last week for possession of pipe bomb components. He was indicted by a federal grand jury in Waco on Tuesday and pleaded not guilty to the charge on Wednesday after agreeing to defer his detention hearing, federal prosecutors said.
State officials have said no evidence linked Reed's arrest to the plant disaster. Federal authorities said they will not speculate on a possible connection.
Reed's lawyer, Jonathan Sibley, said in a statement on Wednesday that Reed denies any involvement in the plant explosion.
"We continue to ask our community to reserve judgment until the facts and evidence are known," Sibley said.
(Editing by Corrie MacLaggan and Sofina Mirza-Reid)