A gas explosion ripped through the headquarters of Mexico’s state-owned oil company, Petróleos Mexicanos (Pemex), on Feb. 1, leaving 37 people dead and hundreds injured. Mexican President Enrique Peña Nieto tweeted regular updates in the hours following the explosion and later called for three days of national mourning. A few days after the incident, the cause was confirmed: a buildup of gas that was ignited by a spark from an electrical fault. Pemex employs over 100,000 people and brings in approximately 37% of state revenue. Last September, 30 people were killed in an explosion at one of the company’s gas plants in northern Mexico.