Washington ? The Obama administration on Thursday doubled its minimum estimate of how much crude oil was gushing from the Deepwater Horizon oil well, saying a panel of scientists had concluded that 20,000 to 50,000 barrels, or as much as 2.1 million gallons, were pouring into the Gulf of Mexico every day before BP sheared the well’s riser pipe on June 3.

That action, which BP engineers undertook to fit a “top hat” containment dome over the well, almost certainly increased the flow, and Dr. Marcia McNutt, the head of the U.S. Geological Survey, said an estimate of the flow since June 3 would be available in a few days.

“Our scientific analysis is still a work in progress,” McNutt said.

The announcement that tens of thousands more barrels of oil than previously estimated have been spewing into the Gulf for weeks added to a growing sense that neither the federal government nor BP correctly assessed the size of the unfolding disaster or marshaled enough resources to meet it.

“It’s hard to keep track of all the false estimates and false promises,” said Jeremy Symons, a senior vice president of the National Wildlife Federation. “The BP gusher is worse than ever, and big nature is losing its battle with big oil.”

Separately Thursday, BP and the Coast Guard acknowledged that their hopes of removing 28,000 barrels of crude from the water daily beginning perhaps next week depend on a largely untested plan to burn more than a third of that oil.

How much oil is flowing from the well has been the subject of heated debate for weeks. BP initially said the well was losing only 1,000 barrels a day, then increased that estimate to 5,000 barrels, a figure that both BP and the Obama administration stuck with for weeks until scientists, examining previously undisclosed video of the spewing oil, testified to Congress that the flow might be as much as 95,000 barrels a day, or nearly 4 million gallons.

The new estimates suggest that despite engineers’ success in capturing an increasing amount of oil — BP said 15,800 barrels of oil was recovered from the well on Wednesday — there seemed to be no reduction in the volume of oil billowing from the well.

This week, Coast Guard Adm. Thad Allen said he hoped to increase the amount recovered from the Gulf to 28,000 barrels a day by pushing the Discoverer Enterprise drill ship past its stated 15,000-barrel-a-day capacity to 18,000 barrels a day, and adding a second vessel, the Q4000, which he said would collect 10,000 barrels a day.

However, BP’s vice president for operations, Kent Wells, said Thursday that all the oil recovered by the Q4000 would be flared, and Allen acknowledged that he’d misspoken Wednesday when he suggested that at least 5,000 barrels would be stored and resold.

Environmentalists and health advocates questioned the decision to burn the crude, saying the burn would produce toxic byproducts that could affect both workers aboard ships in the Deepwater Horizon area and residents in coastal areas. The Q4000, which wasn’t designed to burn crude and is now being fitted with a burner, has a crew of 122, and there are scores of ships in the Deepwater Horizon vicinity, which is beyond the jurisdiction of the Occupational Safety and Health Administration.

“If the weather conditions are such that it’s blowing on shore and local communities are getting that soot, there are a lot of toxic constituents in it,” said Diane Bailey, a senior scientist at the Natural Resources Defense Council.