BP has recovered the blow-out preventer from the floor of the Gulf of Mexico as its internal investigation into the causes of the Macondo well disaster nears a conclusion.The failure of the blow-out preventer led to an explosion on the Deepwater Horizon oil rig that killed eleven people and sparked the worst US environmental disaster ever. BP is expected to release the findings of its internal inquiry within ten days, but having now been brought to the surface, the blow-out preventer will be passed to the US Joint Federal Marine Board and other US agencies independently examining the causes of the spill.Just what happened to the safety device will be a key determinant of ultimate responsibility for the disaster and how much BP eventually has to pay out in compensation and litigation claims.On Friday, BP revealed its bill for cleaning up after the oil spill in the Gulf of Mexico has hit $8bn (£5.2bn), up over £1bn in less than a month, and the relief well is not expected to intercept the broken MC252 well for a couple of weeks. The money so far ahs been spent on the spill response, containment, relief well drilling, the "static kill" operations and claims. On top of this, BP could face an estimated bill of $30bn for compensation and damages.