BP Begins 'Top Kill' Oil Spill Containment, Plugging Well with Mud and Cement

The "top kill" is under way.

BP has begun pumping heavy mud into the blown-out well in the Gulf of Mexico in an attempt to seal it. Cement will follow. The top kill has never before been tried a mile beneath the sea, and company officials say it could be a couple of days before they know whether it is working. BP's top executive has pegged the chance of success at 60% to 70%.

BP began the maneuver, known as a top kill, on Wednesday, amid hopes that injecting heavy drilling fluids deep into the well could stem the relentless flow of oil that has devastated commercial fishing in the Gulf, fouled miles of coastline and put the company and federal regulators at the center of a political firestorm.