WASHINGTON — The government's point man on the Gulf of Mexico oil spill said the catastrophe will persist "well into the fall."

Coast Guard Adm. Thad Allen said Sunday on CBS' "Face the Nation" that the spill will not be contained until the leak at the bottom of the Gulf is fully plugged.

He said that even after that, "there will be oil out there for months to come."

The leak began nearly seven weeks ago after a BP rig exploded and ruptured a wellhead, creating what has become the nation's largest oil spill.

Allen's comments come amid some optimism that a cap placed over the leaking well is allowing significant amounts of oil to be captured.

The containment device began capturing some of the oil late last week and is slowly siphoning off the flow.

BP said the device trapped about 441,000 gallons of oil Saturday, up from 250,000 gallons the day before. And BP Chief Executive Tony Hayward told the BBC Sunday he believes the cap is likely to capture "probably the vast majority" of the oil gushing from the well.

But Allen said on "Fox News Sunday" that he doesn't "want to create any undue encouragement." And he told CNN that nobody should be pleased "as long as there is oil in the water."

Millions of gallons of oil have been rising to the surface and spreading out across the sea. Beaches are being soiled and dead birds and dolphins are washing ashore.

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