BP's latest effort to stem the oil spewing from a ruptured well a mile (1.6 kilometers) deep in the Gulf of Mexico hit a setback when a saw snagged while cutting a riser pipe, officials said Wednesday.
The diamond wire saw being used to cleanly cut off a ruptured riser pipe at the top of a failed blow-out preventer "has become stuck," Coast Guard Admiral Thad Allen told reporters.
"Anybody that's ever used a saw knows every once in a while it will bind up. That's kind of what's happening here," Allen said.
The operation to cut off the leaking riser pipe and then cap it with a replacement unit for the top half of a large valve, known as the blow-out preventer (BOP) stack, is being carried out remotely using underwater robots.
A first cut was successfully made in the leaking pipe overnight, and Allen said he expected the saw would be extracted, or that a new saw would be sent down to the wrecked well head later Wednesday.
Once the riser pipe has been cut off, a "cap" will be lowered over the top of the well head to contain the oil, which will be siphoned up to a drill ship on the surface through a riser extending from the top of the containment unit.
Every attempt so far to plug the leak has failed, and BP has stressed this latest attempt will not stop the flow of oil but only stem it until two relief wells have been drilled. The drill wells are expected to be finished in August.
At least 20 million gallons of oil are estimated to have gushed into the Gulf since the April 20 explosion that sent the Deepwater Horizon rig sinking to the seabed 50 miles (90 kilometers) off the Louisiana coast.
Explore further: Australia set to pay polluters to cut emissions