(CNN) -- The Minerals Management Service, a division within the Interior Department, was a troubled agency long before the oil spill in the Gulf of Mexico and the recent revelations of employee misconduct. The agency -- which oversees U.S. offshore drilling, including the Gulf of Mexico -- has come under fire for mismanagement, questionable conduct and cozy relationships with industry officials. The MMS issued permits for the Deepwater Horizon drill rig -- contracted by BP -- which exploded on April 20. The explosion killed 11 people and resulted in an oil spill that is threatening parts of the Gulf. Interior Department Secretary Ken Salazar, during an appearance Wednesday before the House Committee on Natural Resources, said he was trying to change the agency's culture and its structure, which some critics say leads to mismanagement.
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Minerals Management Service has a troubled history, government reports say
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Report: Inspectors got meals, tickets to sports events from companies they monitored
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Interior Department chief Ken Salazar says he's trying to change MMS culture, structure
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MMS Director Elizabeth Birnbaum has been fired, sources say
At a @placeholder subcommittee hearing Thursday, Salazar insisted Birnbaum had resigned "on her own terms and own volition."