A review of the program published by the department's Bureau of Ocean Energy Management found the "most significant incident" since the start of the program in terms of loss of life was the Nov. 18 accident that killed three of 24 workers on a drilling platform 18 miles off the coast of Louisiana.
The rig was operated by Black Elk Energy, which said the accident occurred during a construction project.
Investigators said rig workers cut into a pipeline on the platform that had oil inside, starting a fire.
In August, Black Elk said a third-party investigation found contractors failed to follow basic safety standards.
The five-year lease period started last year.
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