"BP started pumping heavy mud into the leaking Gulf of Mexico well Wednesday and said everything was going as planned in the company's boldest attempt yet to plug the gusher that has spewed millions of gallons of oil over the last five weeks. BP hoped the mud could overpower the steady stream of oil, but chief executive Tony Hayward said it would be at least 24 hours before officials know whether the attempt worked. The company wants to eventually inject cement into the well to seal it. ""I'm sure many of you have been watching the plume,"" Hayward said of the live video stream of the leak. ""All I can say is it is unlikely to give us any real indication of what is going on. Either increases or decreases are not an indicator of either success or failure at this time.""