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An emergency worker treats an injured worker of Mexico's state-owned oil company PEMEX after an explosion at an adjacent building to the executive tower of PEMEX in Mexico City, Thursday Jan. 31, 2013. A large explosion occurred in the lower floors of the building and dozens have been reported injured so far. (AP Photo/Guillermo Gutierrez)

Mexico City oil company explosion

The Mexican government said on Feb. 4 that a gas leak caused a blast that killed at least 37 people at the offices of state oil monopoly Pemex in Mexico City, raising fresh questions about the firm's safety record.