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BP finishes latest search for Gulf oil leaks

The subsea mission to see if BP's Deepwater Horizon site is leaking oil ended on Saturday, but no results have yet been announced.

The operation, under Coast Guard supervision, began Sunday, Dec. 9, and lasted until Saturday, Dec. 15. The Coast Guard's on-scene coordinator Capt. Duke Walker told CBS News that as of Friday, no leak had been found, but the remotely operated vehicle had not yet inspected the containment dome again, nor had it looked at the main wellhead or the two relief wells at the site.

On Monday, the Coast Guard confirmed the inspection was over, but would not release any information.

Concerns first arose in September when an oil sheen was spotted 50 miles off the Louisiana coast. BP confirmed that the oil was coming from a leaking containment dome that failed to cap the gushing well after the Deepwater Horizon exploded in 2010. BP says the dome now sits abandoned about 1,500 feet from the main well, and that trapped oil was seeping out. The company then plugged the leak in a subsea operation in October.

But more sheens and slicks continued to surface, and BP planned the latest mission to look for the possible source. The mission was put off a week because the underwater vehicle required to make the inspection came from "overseas" and was delayed due to weather, according to Walker.

"That's a problem," says a spokesman for Rep. Ed Markey (D-Mass.)

Markey and Rep. Henry Waxman (D-Calif.) have been asking BP and the Coast Guard for more information and video regarding the recent incidents. Markey's office says the idea that BP has to send for an underwater vehicle from another country, and then wait for it to arrive, speaks to how ill-prepared we may be in the event of another accident like the Deepwater Horizon.

Last month, BP agreed to pay $4.5 billion and pled guilty to 11 counts of felony manslaughter, felony obstruction of Congress and other criminal charges in the Deepwater Horizon explosion back in 2010. BP's then-vice president of exploration for the Gulf of Mexico is charged separately with lying to Congress about how much oil was actually gushing from the blown-out well. CBS News was first to report that both BP and the government were "low-balling" estimates on the oil leak back in 2010.

The Coast Guard's current on-scene coordinator Capt. Duke Walker says that thousands of barrels of oil - each barrel containing 42 gallons - could be trapped in wreckage and equipment from the Deepwater Horizon disaster. The places of "high suspicion" include the containment dome and the so-called riser pipe.

"The other thing [BP] added to the target package this time that we have not looked at previously is the rig wreckage itself, which may contain some small pockets of oil," Walker said.

It's the fourth time BP has gone underwater to look for leaks among the wells and wreckage spanning about a mile, according to Walker. He added that as of Friday, there was no evidence of active leaks from the wells, which he said spewed an estimated 4.9 million barrels of oil in 2010. But he says BP planned to look at the wells again Friday night or Saturday "out of an abundance of caution."

Walker says there could be up to 2,000 barrels of oil (84,000 gallons) in the "riser pipe" in the wreckage, and 1,330 barrels (55,860 gallons) in the containment dome.

So far there has been no attempt to clean up the sheens and slicks spotted since September. The Coast Guard says they pose no risk to the shoreline and that they are difficult to sop up because of their nature, the open waters and effects of the wind.

The Coast Guard has not indicated what the next step would be if no leaks are detected among the Deepwater Horizon wreckage or wells.

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    Sharyl Attkisson is a CBS News investigative correspondent based in Washington.