The funnel-like lid is designed to channel oil for pumping to a surface tanker. The device started pumping gas and oil to the tanker on the surface overnight, but it wasn't clear how much.
A number of colored hoses have been loosely attached to the cap to help combat the near-freezing temperatures and icylike crystals that could clog it.
According to Coast Guard Adm. Thad Allen, they are seeing some progress.
"Progress is being made, but we need to caution against over-optimism," said Allen.
Earlier in the day, Allen guessed that the cap was collecting 42,000 gallons a day - less than one-tenth of the amount leaking from the well. He added that the latest attempt will be, at best, is a temporary and partial fix.
- President Obama arrived for his third visit to the stricken Gulf Coast for a fresh reality check on work to stanch the oil spewing into the Gulf of Mexico. The president underscored his focus on the Gulf by abruptly canceling plans for a trip to Indonesia and Australia later this month.
- U.S. Defense Secretary Robert Gates rejects a more forceful role for the military in plugging the Gulf of Mexico oil leak. Gates says the deep-water disaster is beyond the military's expertise. Gates said Friday that the U.S. military is ready to do whatever it can to respond. But he said there isn't much the military can do beyond providing some manpower.
- Newly disclosed internal Coast Guard documents from the day after the explosion aboard the Deepwater Horizon rig indicated that U.S. officials were warning of a leak of 336,000 gallons per day of crude from the well in the event of a complete blowout. The volume turned out to be much closer to that figure than the 42,000 gallons per day that BP first estimated. Weeks later that was revised to 210,000 gallons. Now, an estimated 500,000 to 1 million gallons of crude is believed to be leaking daily.
- The oil has now reached the shores of four Gulf states - Louisiana, Mississippi, Alabama and Florida - turning its marshlands into death zones for wildlife and staining its beaches rust and crimson in an affliction that some said brought to mind the plagues and punishments of the Bible.
The Associated Press contributed to this report.
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