New Orleans ? The cap on the blown-out well in the Gulf is capturing a half-million gallons a day, or anywhere from one-third to three-quarters of the oil spewing from the bottom of the sea, officials said Monday. But the hopeful report was offset by a warning that the farflung slick has broken up into hundreds and even thousands of patches of oil that may inflict damage that could persist for years.

Coast Guard Adm. Thad Allen, the government’s point man for the crisis, said the breakup has complicated the cleanup.

“Dealing with the oil spill on the surface is going to go on for a couple of months,” he said at a briefing in Washington. But “long-term issues of restoring the environment and the habitats and stuff will be years.”

Allen said the containment cap that was installed late last week is now collecting about 460,000 gallons of oil a day out of the approximately 600,000 to 1.2 million gallons believed to be spewing from the well a mile underwater. In a tweet, BP said it collected 316,722 gallons from midnight to noon Monday.