GRIM SEARCH: Rescuers searched for survivors after an office building blast killed 32 people and injured 121 at the headquarters of Mexico's state-owned oil company, Petroleos Mexicanos, Pemex.
WHY? The cause of the basement explosion in an administrative building next to the 51-story Pemex tower in Mexico City remained a mystery. Early signs pointed to an area that housed electrical and air-conditioning equipment.
WORST TIME: The explosion occurred just as the administrative shift was about to end. It hit the basement and three floors, where as many as 250 people work. The floors collapsed in the 14-story building.