BP says it is trying to seal the blown-out oil well in the Gulf of Mexico by pumping heavy mud into it.
BP said in a news release Wednesday that the "top kill" maneuver has started. 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.
Engineers hope to pump enough mud into the gusher to overcome the flow of the well. Engineers plan to follow up the mud with cement that the company hopes will permanently seal the well.
BP's top executive has pegged the top kill's chance of success at 60 to 70 percent.
Millions of gallons of oil has spewed into the ocean since an April 20 rig explosion.