At least 25 people are dead and more than 100 are injured after an explosion Thursday at the headquarters of state oil company Pemex in Mexico City—while rescuers are desperately searching for more survivors. “An explosion took place in the B2 building of the administrative centre,” the company tweeted. “There are injuries and damage on the ground floor and mezzanine.” The cause is not yet known, but this is the second incident involving the oil giant recently. Just four months ago, 26 people were killed when a Pemex gas plant exploded in northern Mexico. Mexican President Enrique Peña Nieto has called for an investigation into Pemex, which has a 75-year monopoly in the country.