The well isn't dead yet, and it may be back in a flash, officials said as BP began a 48-hour "integrity test" on the well's new sealing cap after 87 days of futile efforts to kill the well by pumping mud into it and putting a top hat on the broken pipe.
As Louisiana's Indian-American Governor Bobby Jindal, leading reporters on a tour of an island one of the worst-hit states is building to stop incoming oil, said: "It would be premature to declare 'Mission Accomplished'."
"This fight's not over for Louisiana," said Jindal worried that public attention and federal help might slacken if the well remains sealed.
The stacking cap, lowered in place earlier this week, has never been deployed at such depths or under such conditions and, therefore, there were no guarantees on how well it would contain the oil, BP said.
In the test, BP closed off - one by one - the valves on the cap system through which oil could escape. If at any time the pressure is deemed too low, meaning that oil is escaping through another source in the breached well, the testing would stop.
BP Chief Operating Officer Doug Suttles told CNN that while no leaks were apparent, "it's way to early to celebrate".
Retired Admiral Thad Allen, who is overseeing the government's response to the spill, said in a statement it "remains likely" that sending the oil to containment ships will be the avenue officials decide to pursue after the test, until the ultimate solution is readied - sealing the well by pumping mud and cement through one of two relief wells being drilled.
The wells are expected to be completed in August. The second one serves as a backup to the first.
Allen said experts also will examine options for shutting off the well again temporarily, if there's a hurricane.
Meanwhile, from state and local officials around the Gulf region, there were warnings that the cleanup from the spill could take years