Top Kill procedure has begun in the Gulf

From ABC News:

BP on Wednesday launched its latest bid to plug the gushing well in the Gulf of Mexico by force-feeding it heavy drilling mud, a maneuver known as a "top kill" that has never before been tried 5,000 feet underwater.

The oil giant's chief executive earlier gave the procedure a 60 to 70 percent chance of working, and President Barack Obama cautioned Wednesday there were "no guarantees."

BP spokesman Steve Rinehart said the company will pump mud for hours, and officials have indicated it may be a couple of days before they know whether the procedure is working. The top kill involves pumping enough mud into the gusher to overcome the flow of the well, and engineers plan to follow it up with cement to try to permanently seal the well.