BP says a "sequence of failures" involving "multiple companies" led to the explosion and fire that killed 11 people and caused a massive Gulf of Mexico oil spill.

In a 193-page report released Wednesday and posted on its website, the company said the accident arose from "a complex and interlinked series of mechanical failures, human judgments, engineering design, operational implementation and team interfaces."

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The internal report was prepared by a team led by BP's head of safety and operations, Mark Bly.