Investigators in the United States say they can't rule out arson as the cause of an explosion in the Texas town of West a month ago.
The April 17 explosion at West Fertilizer Company killed 15 people, wounded 200, and caused a major tremor.
Investigators say an electrical wiring fault or even a broken golf buggy may also have been responsible.
State Fire Marshal Chris Connealy told a press conference there had been reports of faulty golf buggy batteries sparking fires, and as the brake pad and an axle from a golf cart been found at the scene, that could not be ruled out as a cause, the BBC reports.
Authorities had said earlier there was no indication the fire was anything other than an industrial accident.
The flames destabilised a tank of ammonium nitrate which then exploded when struck by falling equipment, officials told the news conference, adding that the chain reaction caused a much larger quantity of the chemical to detonate.
