Petroleos Mexicanos workers talk about the debris at the Pemex... Nieuwsfoto'sAdministrateur,Benzine,Beroep,Beveiliging,De media,Energie-industrie,Exploderen,Financiën,Horizontaal,Mexico,Mexico-Stad,Noord- & Zuid-Amerika,Noord-Amerika,Ongelukken en rampen,Petroleos Mexicanos,Praten,Verenigde StatenPhotographer Collection: Bloomberg 2013 BloombergPetroleos Mexicanos (Pemex) workers talk about the debris at the Pemex administrative building in Mexico City, Mexico, on Sunday, Feb. 3, 2013. The search for the cause of a blast that destroyed three floors of a building at Pemex' headquarters and killed at least 34 people entered a fourth day, as investigators toiled ahead of a self-imposed deadline for finding an answer. Photographer: Susana Gonzalez/Bloomberg via Getty Images