Gulf Coast residents are anxiously awaiting word on whether the latest BP remedy to plug the gushing oil well off Louisiana works.
If oil stops flowing to the surface in the Gulf of Mexico, BP officials will know the effort was successful.
BP is pumping heavy mud into the leaking well, and executives say there have been no problems so far.
Yesterday, BP Chief Executive Tony Hayward said engineers would not know until at least this afternoon whether the latest remedy was having some success.
If the risky procedure, known as a top kill, stops the flow, BP would then inject cement into the well to seal it. The top kill has worked above ground but has never before been tried 5,000 feet beneath the sea. BP has pegged its chance of success at 60 to 70 percent.