Deepwater Horizon rig
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Light shed on Gulf of Mexico oil spill causes

14 September 2011 Last updated at 17:24 BST

The central cause of the blowout that caused last year's massive Gulf of Mexico oil spill was the failure of a cement barrier casing, according to a report by US federal investigators.

The report also blames the BP disaster on poor risk management, a last minute change of plan and the failure to respond to critical indicators.

The BBC's Adam Brookes in Washington says the report also questions the whole regulatory framework governing deep sea drilling off the US coast.