BP: Mud pumped into well is holding back the oil

BP's latest attempt to seal up the leaking oil well in the Gulf of Mexico -- the so-called "static kill" that involved pumping mud into the blown out well -- appears to be working.

As of Wednesday morning the flow of crude oil had stopped, a significant development after more than three months of problems and millions of litres of leaked oil.

Workers pumped mud into the well for about eight hours Tuesday until it reached a "static condition." Officials are now monitoring the well to ensure it remains stable.

"It's a milestone," BP PLC spokeswoman Sheila Williams said. "It's a step toward the killing of the well."

The oil spill first began on April 20 with a deadly explosion on the offshore Deepwater Horizon oil rig off the coast of Louisiana, which killed 11 workers.

Depending on what happens next, workers may cap the well with a plate of cement to further seal the leak.

Shortly after the static kill procedure began on Tuesday there were positive signs. Pressure in the well dropped quickly in the first hour-and-a-half, which was a sign officials were hoping for.

Sealing the well is a two-step process. Once the static kill is complete, the next phase will involve an 18,000 relief well that is being drilled into the bottom of the well.

Once that access point is complete, a so-called "bottom kill" will commence. Officials will then pump concrete and mud into the bedrock to finish the job.

"There should be no ambiguity about that," said retired Coast Guard Adm. Thad Allen. "I'm the national incident commander, and this is how this will be handled."

On Wednesday the U.S. government appeared to launch a PR initiative, with White House energy advisor Carol Brown appearing on morning talk shows to say that three quarters of the oil from the spill has been cleaned up or broken down naturally.

Brown, who welcomed the latest developments in BP's efforts, said a new assessment of the environmental impact found that 75 per cent of the oil had been cleaned, collected, evaporated or broken down.