Workers clean up debris at the Petroleos Mexicanos headquarters building in Mexico City, Mexico, on Tuesday, Feb. 5, 2013. Mexican authorities said a buildup of gas led to the blast last week that killed 37 people at Petroleos Mexicanos's headquarters, the first official attempt to explain the nation's deadliest explosion since 2006. Photographer: Susana Gonzalez/Bloomberg via Getty Images
{"Image ImageDescription": "Workers clean up debris at the Petroleos Mexicanos headquarters building in Mexico City, Mexico, on Tuesday, Feb. 5, 2013. Mexican authorities said a buildup of gas led to the blast last week that killed 37 people at Petroleos Mexicanos?s headquarters, the first official attempt to explain the nation?s deadliest explosion since 2006. Photographer: Susana Gonzalez/Bloomberg via Getty Images", "Image Copyright": "2013 Bloomberg"}