BP's risky bid to plug a Gulf of Mexico well appears to be working, but new data shows it is already the worst oil spill in US history with a huge slick fouling the seas.
US officials say for the first time since an April 20 explosion ripped through a BP-leased rig, the oil leak seems to have stopped, but the glimmer of good news is too late to avert an environmental catastrophe.
Obama holds BP accountable for spill
Even if the BP's "top kill" manoeuvre succeeds in capping the leak, millions of gallons of crude are sloshing about in the Gulf waters, and a visibly angered President Barack Obama has moved to rein in the oil industry.
The US President barred any new deepwater oil exploration for six months and suspended some permits and lease sales off the vulnerable coasts of Alaska and Virginia.
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The president also lashed out at BP, suggesting it may have sought to downplay the true extent of the economic and ecological disaster now threatening the southern states of Louisiana, Alabama and Mississippi as well as Florida.
New data released by government scientists said the oil may have been flowing at a rate up to four times higher than previously estimated by BP.
Worst oil spill in US history
The new estimates suggested the oil was gushing out at a rate of between 12,000 to 19,000 barrels a day - much higher than the previous estimate of 5000 barrels a day.
Under such a scenario, that would mean between 18.6 million gallons and 29.5 million gallons of oil have seeped into the Gulf - way higher than the 11 million gallons of crude spilled in the 1989 Exxon Valdez disaster off Alaska.
With 160km of Louisiana coastline already contaminated, there are fears US officials may order the burning of the state's unique marshlands, home to a variety of endangered birds and mammals.
"If they do that they've killed everything,"
Margaret Curole, a spokeswoman for a commercial fishermen's association, bursting into tears. "It's everything we love disappearing."
BP and the government have been heavily criticised for failing to get the spill under control.
Obama under fire
Obama dismissed charges the government response had been too slow.
But he said it was legitimate to question whether the British energy giant was "being fully forthcoming about the extent of the damage".
Coast Guard chief Thad Allen, coordinating the US government's battle against spill, said the top kill manoeuvre launched on Wednesday by BP to plug the leak had stopped the gush of oil from the 1600m-deep well.
But he cautioned it was still too early to declare victory as BP pumps heavy drilling liquids, dubbed mud, into the fractured wellhead to beat back the flow of oil, before sealing it with concrete.
"They've been able to stabilise the wellhead, they're pumping mud down it.
They've stopped the hydrocarbons from coming up," Allen told local radio WWL First News.
In a new development all 125 commercial fishing boats helping to clean up the oil off Louisiana's Breton Sound were recalled after four workers reported health problems.
The crew members aboard three separate vessels in the area reported nausea, dizziness, headaches and chest pains, officials said.
