The "greatest environmental disaster" in U.S. history -- which has appeared at times to leave a high-control White House powerless -- seemed to have lost its power to scare.

A few hours after BP's well was declared virtually dead, the Obama administration announced Wednesday that only about 26 percent of the oil spilled in the Gulf of Mexico was unaccounted for.

"A significant amount of this," said Jane Lubchenco, head of the National Oceanic and Atmospheric Administration, "is a direct result of the very robust federal response efforts."

But, in interviews, scientists who worked on the report said the figures were based in large part on assumptions and estimates with a significant margin of error.

Some outside scientists went further: In a situation in which many facts remain murky, they said, the government seemed to have used interpretations that made the gulf -- and the federal efforts to save it -- look as good as possible.

"There's a lot of . . . smoke and mirrors in this report," said Ian MacDonald, a professor of biological oceanography at Florida State University. "It seems very reassuring, but the data aren't there to actually bear out the assurances that were made."

The government's accounting of the spilled oil, called an "oil budget," was announced Wednesday at the White House. It appeared to answer the most troubling question: Of the 4.9 million barrels (205.8 million gallons) that poured out of the well, only 827,000 barrels were siphoned to vessels on the surface. Where did the rest of it go? Where there had been mystery, now there was a pie chart.

It showed that 5 percent of the total oil had been burned and that 3 percent had been skimmed off the surface. An additional 25 percent had evaporated or dissolved. About another quarter had been "dispersed" -- broken into tiny droplets by chemicals or by the force of being blasted out of the well.

The dispersed oil, Lubchenco said, "is in the process of being very rapidly degraded naturally, and so Mother Nature is assisting here considerably." She said, however, that "diluted and out of sight doesn't necessarily mean benign."

Those facts did not seem to support a statement that White House climate and energy czar Carol M. Browner made Wednesday on NBC's "Today" show. An initial assessment showed that "more than three-quarters of the oil is gone. The vast majority of the oil is gone," she said. At best, the report shows that three-quarters of the oil could be on its way out: It does not say that it has vanished.

The remaining 26 percent or so of the oil was still unaccounted for, although Lubchenco said that did not necessarily mean it is still causing ecological harm.

Asked how much of the success of the cleanup should be attributable to BP, White House press secretary Robert Gibbs said the cleanup "would have been different" if federal officials had not pushed the company to work faster.