Updated 7:33 p.m. ET
No more oil is likely to leak into the polluted Gulf of Mexico, the government's pointman on the massive oil spill declared Wednesday as efforts to plug a blown-out well succeeded. A relieved President Barack Obama said the fight to stop the leak is "finally close to coming to an end."
At the White House, National Incident Commander Adm. Thad Allen said the effort to plug the leak was progressing, giving officials "high confidence" that there will soon be no more oil leaking into the environment. That upbeat assessment came as a government report released Wednesday said only about a quarter of the spilled oil remains in the Gulf. The rest has been contained, cleaned up or has otherwise disappeared.
Obama's team, however, was careful to emphasize that much work remains, from cleanup to damage assessment to help for hurting families.
"There's a lot of reasons why there's no 'Mission Accomplished' banner," White House spokesman Robert Gibbs said. "There's a lot of work to do. ... We're not leaving the area, and more importantly, we're not leaving behind any commitment to clean up the damage that's been done and repair and restore the Gulf."
Government officials defended the credibility of the report that says about 75 percent of the oil is gone - though what's left is still nearly five times the amount that poured from the Exxon Valdez. They said that description is based on direct measurements of the spill and estimates, and that the instruments they've used to capture the scope of the disaster have improved since it began.
CBS News Correspondent Mark Strassmann reports from the Gulf of Mexico that about 26 percent of the leaked oil actually ended up in the water or along the shoreline, according to a new government study. In places like Grand Isle, La., residents said that BP is already cutting back cleanup crews and that they resent it.
BP PLC reached what it called a significant milestone overnight when mud that was forced down the well held back the flow of crude. That means the procedure known as a "static kill" appears to be working, though crews now must decide whether to follow up by pumping cement down the broken wellhead.
Federal officials won't declare complete victory until they also pump in mud and then cement from the bottom of the well, and that won't happen for several weeks.
"We've pretty much made this well not a threat, but we need to finish this from the bottom," Allen told WWL-TV in New Orleans.
Allen said at the afternoon press conference that the pressure in the capped well and surrounding water have equalized and he has "high confidence that there will be no oil leaking into the environment."
He said scientists were still discussing whether or not cement would be used in the final sealing of the well, depending on the condition of the drill pipe.
President Barack Obama on Wednesday applauded the headway, saying the Gulf of Mexico operation is "finally close to coming to an end."
He said people's lives "have been turned upside down" as a result of the April 20 BP oil spill, but said he was heartened by indications the spill is, at last, being brought under control.
About, according to a report to be released Wednesday by scientists with the Interior Department and National Oceanic and Atmospheric Administration.
At the press conference, Gibbs refuted a reporter's assertion that BP CEO Tony Hayward might deserve an apology because - in the reporter's words - Hayward was right when he said that the oil spill was insignificant because the volume of oil released is insignificant compared to the volume of the ocean as a whole.
"Nobody owes Tony Hayward an apology," Gibbs said. "Any apology that is owed is to the disruption to the lives of families, fishermen, hotel owners."
A little more than 205 million gallons gushed in total from the well, based on government estimates.
That leaves about 53.5 million gallons in the Gulf. The amount remaining - or washed up on the shore - is still nearly five times the size of the 11 million-gallon Exxon Valdez spill, which wreaked environmental havoc in Alaska in 1989.
About a quarter of the oil evaporated or dissolved in the warm Gulf waters, the same way sugar dissolves in water, federal officials said. Another one-sixth naturally dispersed because of the way it leaked from the well. Another one-sixth was burned, skimmed or dispersed using controversial chemicals.
Charter boat captain Randy Boggs, of Orange Beach, Ala., said Wednesday he has a hard time believing BP's claims of success with the static kill and similarly dismissed the idea that only a quarter of the oil remains in the Gulf.
"There are still boats out there every day working, finding turtles with oil on them and seeing grass lines with oil in it," said Boggs, 45. "Certainly all the oil isn't accounted for. There are millions of pounds of tar balls and oil on the bottom."
A 75-ton cap placed on the well in July has been keeping the oil bottled up inside over the past three weeks but was considered only a temporary measure. BP and the Coast Guard wanted to plug up the hole with a column of heavy drilling mud and cement to seal it off more securely.
The static kill - also known as bullheading - involved slowly pumping the mud from a ship down lines running to the top of the ruptured well a mile below. A previous, similar effort failed in May when the mud couldn't overcome the unstemmed flow of oil.
The pressure in the well dropped quickly in the first 90 minutes of the static kill procedure Tuesday, a sign that everything was going as planned, wellsite leader Bobby Bolton told The Associated Press. Bolton said Tuesday night that the procedure was going well. "Pressure is down and appears to be stabilizing," he told the AP then.
Assistant to the President for Energy and Climate Change Carol Browner told CBS' "The Early Show" that it was good news that the static kill was working but that "we remain focused on the relief well."
"That is the way to permanently kill this well. That's what we want to see happen."
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.
In the Gulf, workers stopped pumping mud in after about eight hours of static kill work and were monitoring the well to ensure it remained stable, BP said.
"It's a milestone," BP PLC spokeswoman Sheila Williams said. "It's a step toward the killing of the well."
The pressure in the well dropped quickly in the first 90 minutes of the static kill procedure, a sign that everything was going as planned, wellsite leader Bobby Bolton told The Associated Press on Tuesday.
BP has said the static kill might be enough by itself to seal the well. But the 18,000-foot relief well that BP has been drilling for the past three months will be used later this month to execute the "bottom kill," in which mud and cement will be injected into the bedrock 2½ miles below the sea floor to finish the job, Allen said Tuesday.
"There should be no ambiguity about that," Allen said. "I'm the national incident commander, and this is how this will be handled."
The task is becoming more urgent because peak hurricane season is just around the corner, Allen said. Tropical Storm Colin formed then dissipated far out in the Atlantic on Tuesday, but early forecasts say it will travel toward the East Coast rather than the Gulf.