The disaster was a major setback to a safety record that had been improving following a series of incidents in the 1980s and 1990s, according to company figures. The number of accidents per million hours worked dropped by more than half, from 1.06 in 2005 to 0.42 in 2010. That is in line with the international average of about 0.43 per million, according to the U.K.-based International Association of Oil and Gas Producers, which does not independently verify company numbers.
But Pemex acknowledged in a report that starting in late 2011, a series of smaller blasts and fires, mainly at refineries and petrochemical plants, had "seriously impacted" its safety rate. It said the rate of injuries per million hours had risen to 0.54.
As part of the federal government, Pemex is entirely responsible for inspecting its own buildings. Murillo said investigators were looking into the records of building inspections, and why they had not discovered the accumulation of gas.
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