Update: Coast Guard changes statement, no proof of success yet

Update (below): Coast Guard chief claims, 'They've stopped the hydrocarbons'

Update (click for story): Reuters says oil command can't confirm leak stopped, though Admiral adds to his statement on NPR

'Cautiously optimistic' but won't say well is capped

Admiral Thad Allen, head of the government's effort to help staunch the oil leak that resulted after an offshore rig collapsed into the Gulf of Mexico, told reporters Thursday morning that BP's latest effort to plug the leak has succeeded, according to the Chicago Tribune (and Los Angeles Times).

The so-called "top kill" effort, launched Wednesday afternoon by industry and government engineers in Houston, has pumped enough drilling fluid to block all oil and gas from the well, Allen said. The pressure from the well is very low, but persistent, he said.

Once engineers have reduced the well pressure to zero, they will begin to pump cement into the hole to entomb the well. To help that effort, he said, engineers are also pumping some debris into the blowout preventer at the top of the well.

Allen said one ship that was pumping fluid into the well has run out of the fluid, or "mud," and that a second ship is on the way. He said he was encouraged by the progress.

"We'll get this under control," he said.

"They've stopped the hydrocarbons from coming up," National Incident Commander Thad Allen was quoted elsewhere as saying. "They've been able to stabilize the well head, they are pumping mud down it."

Allen repeated his assertion on NPR Thursday morning, but officials close to the spill wouldn't confirm or deny Allen's comments to Reuters.

NOLA.com said: "Admiral Thad Allen said gas and oil is no longer blowing out of the wrecked well on the sea floor as BP engineers and contractors pumped thousands of gallons of heavy mud down the well hole overnight Wednesday and early Thursday."

As of early Thursday morning, the New York Times and the Wall Street Journal were still reporting that results of the "top kill" remained uncertain. An article carried by the LA Times and The Chicago Tribune reported the stopped leak news; both papers are owned by the same parent company.

MarketWatch, reporting on the LA Times story, wrote: "Coast Guard Admiral Thad Allen said Thursday that BP's effort to plug its leaking oil well through its "top kill" procedure appears to be working, according to a report by The Los Angeles Times. The oil continues to flow, but at lower pressure. Allen also said the government is preparing to release an esimate of the amount of oil that has been leaking from the well. Official estimates have been at 5,000 barrels a day, but others have said the leak is worse. "

Said the Journal:

"The absence of any news is good news,'' said Coast Guard Admiral Thad Allen, who is overseeing the operation. He added: "It's a wait and see game here right now, so far nothing unfavorable"....

Top kills were used to plug wells in Kuwait that were sabotaged by the withdrawing Iraqi army during the Persian Gulf War of 1990-91. But the technique has never before been attempted in waters of such depth; the mouth of the Deepwater Horizon well lies nearly a mile beneath the ocean's surface.

"We'll determine over the next 24 hours whether that plan has been successful," Doug Suttles, chief operating officer of BP, said at an evening news conference.

Coast Guard Rear Adm. Mary Landry said she was "very encouraged" but added, "I do not want to express optimism until we know for sure" that the procedure is working.

If Allen's assertion -- and the reporting of his statement -- is correct, the "top kill" effort will have stopped an oil leak that went on for five weeks and spewed millions of gallons of oil into fragile gulf waters. BP, which was responsible for the leaking drillbore, also pumped an unknown volume of chemicals into the ocean to disperse the spill.

Ecological damage, and the total volume of spilled oil, remains unknown.

As of early Thursday morning, the New York Times was still reporting that results of the "top kill" remained uncertain. An article carried by the LA Times and The Chicago Tribune reported the stopped leak news; both papers are owned by the same parent company.

Late Wednesday, an Alabama news station alleged that fluid seen on a live video feed may have been mud and not oil. The well continues to show pressure; the job won't be complete until the well site is entombed in cement, Allen claimed Thursday.

What you see spewing from the well in the Gulf tonight may not be oil, but drilling mud. BP Spokesperson Doug Suttles says that's what it looks like but, there's no way to know without testing it. From the looks of things, they say so far...so good.

Suttles says, "The job has been proceeding according to plan. We started pumping operations at 1 o'clock this afternoon. We pumped over seven thousand barrels of drilling mud so far, at varying rates but up to 65 barrels a minute."