Investigation finds no evidence of explosives in the blast the decimated several floors of building in Mexico City.
MEXICO CITY—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 headquarters, Mexico’s attorney general said.
But Attorney General Jesus Karam said investigators were still looking for the source of the gas, and revising records of building inspections to determine why Petroleos Mexicanos had not discovered the gas accumulation. As a state company, Pemex is responsible for inspecting its own buildings.
An investigation by Mexican, Spanish, US and British 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 in Mexico City.
He said the investigators believe that an electrical spark or other source of heat had detonated the gas.
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 said. 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.
Murillo said officials had yet to discover the source of what initial evidence indicated to be methane gas that leaked from a duct or tunnel or came from the sewer system and built up in the basement of the building.
Murillo said that an independent contractor had told investigators that he was working with a crew of three men performing maintenance in the basement of building B2. The contractor said the basement wasn’t lit, so his crew had rigged illumination by attaching a crude electric cable to a power source in the ceiling.
The contractor told investigators that seconds after he moved to a higher floor, he heard a noise and then the building was rocked by an explosion. The three men were found dead in the lower basement with burn marks, one with a fragment of cable stuck to his body. They had no evidence of the dismemberment typical in the detonation of explosives.
Murillo described the blast as a “diffuse” explosion whose blast moved slowly and horizontally, typical of the detonation of a cloud of gas, rather than an explosion that would have emanated from a relatively compact source like a bomb.
He said laboratory tests had turned up “zero” evidence of any explosive.
“We’ve been able to determine that the explosion was caused by an accumulation of gas in the basement of the building,” he said. “This explosion, at its peak, generated an effect on the structures of the floors of the building, first pushing them up and then causing them to fall, and that was the primary cause of deaths in the building.”
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