NEW ORLEANS — BP finally choked off the flow of oil into the Gulf of Mexico on Thursday — 85 days and up to 184 million gallons after the crisis unfolded — then began a tense 48 hours of watching to see whether the capped well would hold or blow a new leak.
To the relief of millions of people along the Gulf Coast, the big, billowing brown cloud of crude at the bottom of the sea disappeared from the underwater video feed for the first time since the disaster began in April, as BP closed the last of three openings in the 75-ton cap lowered onto the well earlier this week.
"Finally!" said Renee Brown, a school guidance counselor visiting Pensacola Beach, Fla., from London, Ky. "Honestly, I'm surprised that they haven't been able to do something sooner, though."
But the company stopped far short of declaring victory over the biggest offshore oil spill in U.S. history and one of the nation's worst environmental disasters, a catastrophe that has killed wildlife and threatened the livelihoods of fishermen, restaurateurs and oil industry workers from Texas to Florida.
Now begins a waiting period during which engineers will monitor pressure gauges and watch for signs of leaks elsewhere in the well. In the worst-case scenario, pressure from the rising oil could fracture the well and cause leaks to erupt across an area of the seafloor too large to cap.
If engineers see any sign of a new leak, the cap will be reopened, allowing oil to spill into the sea again.
Even if the well holds out for the whole two days, the vents will be opened again and oil released while engineers conduct a seismic survey of the ocean floor to make sure oil and gas aren't breaking out of the well into the bedrock, said retired Coast Guard Adm. Thad Allen, the Obama administration's point man on the disaster.
"For the people living on the Gulf, I'm certainly not going to guess their emotions," BP vice president Kent Wells said. "I hope they're encouraged there's no oil going into the Gulf of Mexico. But we have to be careful. Depending on what the test shows us, we may need to open this well back up."
Either way, the cap is only a temporary fix until a relief well can be drilled into the bedrock and cement and mud can be pumped into the broken well deep underground, creating a seal that will hold more securely. BP expects to complete a relief well by mid-August, and perhaps as early as the end of this month.
Thursday's news elicited joy mixed with skepticism from wary Gulf Coast residents following months of false starts, setbacks and failed attempts. Alabama Gov. Bob Riley's face lit up when he heard the oil flow had stopped.
"That's great. I think a lot of prayers were answered today," he said.
"I don't believe that. That's a lie. It's a (expletive) lie," said Stephon LaFrance, an oysterman in Louisiana's oil-stained Plaquemines Parish who has been out of work for weeks. "I don't believe they stopped that leak. BP's trying to make their self look good."
President Barack Obama called it a positive sign, but cautioned: "We're still in the testing phase."
The stoppage came 85 days, 16 hours and 25 minutes after the first report April 20 of an explosion on the BP-leased Deepwater Horizon oil rig that killed 11 workers. Somewhere between 94 million and 184 million gallons spilled into the Gulf, according to government estimates.
The breakthrough came after a string of failed attempts by BP to contain the leak, including the use of a giant concrete-and-steel box that became clogged with ice-like crystals; a colossal stopper and siphon tube that trapped very little oil; and an effort to jam the well by pumping in mud and shredded rubber.
Wells said the oil stopped flowing into the water at 2:25 p.m. CDT after engineers gradually dialed back the amount of crude escaping through the last of three vents in the cap, an 18-foot-high metal stack of pipes and valves.
On the video feed, the violently churning cloud of oil and gas coming out of a narrow tube thinned, and tapered off. Suddenly, there were a few puffs of oil, surrounded by cloudy dispersant BP was pumping on top. Then, there was nothing.
"I am very pleased that there's no oil going into the Gulf of Mexico. In fact, I'm really excited there's no oil going into the Gulf of Mexico," Wells said.
BP stock, which has mainly tumbled since the spill began, closed nearly 8 percent higher on the New York Stock Exchange after the news.
The cap is designed to stop oil from flowing into the sea, either by bottling it up inside the well, or capturing it and piping it to ships on the surface. Allen said if the cap holds, it will probably be used to pipe oil to the surface, with the option of employing it to shut the well completely if a hurricane threatens.
The testing of the cap went ahead after a daylong day imposed by the federal government because of last-minute fears that the operation would cause a rupture that could make the disaster worse.
Even if the cap works, this is not the end of the crisis by any means. The drilling of the relief wells continues. After that, the Gulf Coast faces a monumental cleanup and restoration that could take years.
"It feels good, but I mean, the damage is already done. That's the problem," said a somber Manuel Meyer, a deckhand helping to unload and box blue crabs in Hopedale, La. "I mean, they can clean it up, but they're finding oil popping up everywhere." He added: "It's going to continue for several years, several years, and it ain't going to do nothing but get worse before it gets better."
Nine-year-old Lena Durden threw up her hands in jubilation when her mother told her the oil was stopped.
"God, that's wonderful," said Yvonne Durden, a Mobile-area native who now lives in Seattle and brought her daughter to the coast for a visit. "We came here so she could swim in the water and see it in case it's not here next time."
Randall Luthi, president of the Washington-based National Ocean Industries Association, a trade group representing the offshore oil industry, said: "This is by far the best news we've heard in 86 days. You can bet that industry officials and their families are taking a big sigh here."