A gas buildup ignited by an electrical spark or other heat source caused the blast that killed 37 people and wounded dozens of others last week at the state oil company's Mexico City headquarters, Mexico's attorney general says. Investigators are still looking for the source of the gas, and reviewing records of building inspections to determine why Petroleos Mexicanos had not discovered the gas accumulation.
An investigation by Mexican and international experts into the petroleum giant's worst disaster in more than a decade found no evidence of explosives in the blast that collapsed several lower floors of the Pemex administrative building, the attorney general says. With the exception of three victims, none of those killed had the burn marks or damaged ear drums that are typical evidence of a bombing, he says. Nor was there any sign of a crater or fracturing of the building's steel beams, also common signs of the detonation of an explosive device. (Read more Pemex stories.)