This image taken from video released by BP LLC shows equipment being used in the efforts to cap the Deepwater Horizon oil well in the Gulf of Mexico, Thursday, June 3, 2010.
BP reported some oil was flowing up a pipe Friday from a cap it wrestled onto its broken Gulf of Mexico well but crude still spewed and it was unclear how much could be captured in the latest bid to tame the nation's worst oil spill.
In a process that began Tuesday, officials were trying a cut-and-cap of the leaking well-site, which lies 1,500 metres below sea level off the shore of Louisiana.
The goal was to slice off the broken riser pipe, which had connected the well to a rig at the surface before the rig's collapse in April, in a smooth cut. A cap, with a rubber seal, would then be placed over the new opening to collect a portion of the leaking oil, lowering the fallout until a permanent solution is achieved.
In a brief statement Thursday evening, Admiral Thad Allen, the National Incident Commander and top American official dealing with the spill, confirmed the cap was in place.
Live television images, however, showed oil continuing to leak heavily, leaving it unclear whether the cap had been sealed and how effective it might be.
BP's Chief Operating Officer Doug Suttles said it will be later in the day before they know how much is being captured.
"There is flow coming up the pipe. Just now, I don't know the exact rate," Suttles said on NBC's "Today" show.
Robots a mile beneath the Gulf positioned the lid over the main pipe on the leaking well Thursday night. Live video footage, though, showed that the oil seemed unimpeded.
"The placement of the containment cap is another positive development in BP's most recent attempt to contain the leak. However, it will be some time before we can confirm that this method will work and to what extent it will mitigate the release of oil into the environment," Adm. Allen said in the statement.
"Even if successful, this is only a temporary and partial fix, and we must continue our aggressive response operations at the source, on the surface and along the Gulf's precious coastline."
Earlier in the day, Adm. Allen revealed that the effort to cut the pipe, which had been delayed when a saw jammed, had been successful.
"For the first time in a couple of days, I have some good news," he said earlier Thursday.
To achieve the cut, however, crews had to use heavy-duty cutters that aren't as precise as the saw they'd first hoped to use. The rougher cut will lead to a poorer seal with the cap, and higher leakage of oil into the ocean. The government estimated last week that between 12,000 and 19,000 gallons a day were leaking.
"It will be a little bit more challenging to get the seal around, but we will have a containment device there - and we'll be able to capture more oil than we would otherwise - and we're going to have to see as we put the containment cap on exactly how effective it is," Adm. Allen said.
The cut was also expected to increase the amount of oil spilling into the ocean, by as much as 20 per cent, but was necessary to try and fit a cap over the high-pressure well - a process likened to forcing a funnel onto an open fire hydrant valve, against the pressure of water.
Adm. Allen is scheduled to provide another update early Friday morning, a day that President Barack Obama is due to arrive in the region. It will be the president's third visit since the spill began.
In an interview with CNN's Larry King Thursday evening, Mr. Obama said he is "furious" with the situation, and continued to calmly say the responsibility was BP's.
"BP caused this spill. We don't yet know exactly what happened. Whether it's a combination of human error, them cuttin' corners on safety, or a whole other variety of variables, they're responsible. So, they've got to pick up the tab," Mr. Obama said, in an interview that also covered such topics as his approval ratings and which NBA team he felt superstar LeBron James should sign with this summer.
His calm interview with Mr. King led some pundits to continue to question whether the president has been "angry enough" at the oil company's inability to cap the spill, which began after an explosion at the Deepwater Horizon rig on April 20.
But the president's continued blame of BP is part of a broader effort by his administration to distance itself from the oil company.
Other recent moves include the cancellation of joint government-BP press conferences that had taken place six days a week since late April, and the White House's high-profile delivery of a $69-million bill to BP earlier Thursday.
The cut-and-cap effort is the latest in a series of efforts to slow the leak. First, the company tried a large dome to collect leaking oil and funnel it to the surface. It clogged with icicle-like formations and failed.
They later tried a smaller cap, which failed. They tried inserting a hose into the pipe, and a "top kill," which was meant to clog the pipes. Both also failed.
The only surefire way to stop the leaking well is to drill a second well, and then inject heavy mud and material to jam the leaking well from below. Two relief wells are currently being dug with the hope of one succeeding, but neither is expected to be finished before August.
"Look, we've got a couple of tasks right now. Number one, BP has to shut down this well. The only guarantee for shutdown is the relief well and that's going to take a couple of months," Mr. Obama told Mr. King. "In the meantime, we hope by cutting the riser, and putting a cap on this thing they can funnel up the oil. And that will help."
With files from AP