The explosion that killed 37 people at the Mexico City headquarters of state oil monopoly Pemex in January was caused by a build-up of methane gas and solvent vapors, an official investigation has found.
Methane from the soil beneath the building rose up into the basement where it combined with the vapor of solvents used in maintenance work, according to the official report released last Friday. The investigation found that the methane would not have built up in the basement if the building had had proper ventilation.
The initial spark that set off the blast was likely caused by an electronic device such as a light cable extension, a lamp or a plug. Over 100 people were injured as several floors of the 54-story building collapsed as a result of the explosion.