"It's going to be good news in a time where there hasn't been a lot of good news," said Retired Coast Guard Adm. Thad Allen.
But the job isn't over yet.
Engineers are still trying to firm up the now-plugged leak through a relief well. Allen, the national incident commander, said pumping mud down the blown-out well stopped the immediate threat, but engineers will still pump mud and cement through a relief well later this month to permanently plug the underground reservoir that has been feeding the gusher.
Allen said BP and the federal government still face work in the recovery phase.
Government numbers released this week show 5 million barrels of oil spilled were by far the most in history, but according to a report by scientists with the Interior Department and National Oceanic and Atmospheric Administration, only about one-quarter of the BP oil that spilled out of its broken well remains in the Gulf.
Nearly three-quarters of the oil - more than 152 million gallons - has been collected at the well by a temporary containment cap, been cleaned up or chemically dispersed, or naturally deteriorated, evaporated or dissolved.
However, local fishermen remain skeptical.
- White House energy adviser Carol Browner said on morning TV talk shows that a new assessment found that about 75 percent of the oil has either been captured, burned off, evaporated or broken down in the Gulf.
- Workers stopped pumping mud in after about eight hours of their "static kill" procedure and were monitoring the well to ensure it remained stable, BP said.
- Mud that was forced down the broken wellhead to permanently plug the gusher is only half the story. To call the mission a success, crews working on a flotilla of vessels on a desolate patch of water need to seal off the well from two directions.
- An 18,000-foot relief well BP has been drilling for the past three months will be used later this month to execute a "bottom kill," in which mud and cement will be injected into the bedrock 2½ miles below the sea floor to finish the job, retired Coast Guard Adm. Thad Allen said.
- BP won't know for certain whether the static kill has succeeded until engineers can use the soon-to-be-completed relief well to check their work.
The Associated Press contributed to this report.