Officials still don't know what caused last month's massive explosion at a fertilizer plant in West, Texas, despite weeks of collecting evidence—300,000 pounds of corn were sifted through by hand—and a $1 million investigation.
The blast, which killed 14 people and injured more than 200 on April 17, was triggered by a fire that was reported 20 minutes before the explosion. Though four causes for the blaze were ruled out at the beginning of the investigation, state and federal officials haven't made much progress since then. As of Thursday, the cause of the fire was officially ruled "undetermined"—with foul play still a possibility. However, authorities are hesitant to make any bold statements, as Reuters notes:
Robert Champion, a special agent in charge at the Bureau of Alcohol, Tobacco, Firearms and Explosives, said that while authorities could not rule out arson, they also could not eliminate the plant's electrical system or a golf cart at the plant as potential causes.
The cause of the fire will remain officially "undetermined" if not enough evidence is available to eliminate multiple causes.
But while the scene investigation may be complete, the criminal investigation is just beginning. Last week, law officials announced that they launched a criminal probe in their investigation on the very same day they arrested Bryce Reed, a 31-year-old paramedic who was among the first to respond to the explosion, for possessing pipe bomb-making materials. Reed pleaded not guilty to the charges on Wednesday. At this time, authorities won't comment on whether they believe there is any connection between Reed and the explosion.