BP plans to slowly increase the amount of oil and gas flowing up the pipe
The oil company BP says it has successfully started to siphon oil from its leaking Gulf of Mexico well to a tanker on the surface.
BP executive Kent Wells would not say how much oil was being siphoned but said the process was "working well".
BP succeeded on its third attempt to insert a long narrow tube into the leaking pipe, using underwater robots.
Earlier, scientists said they had found vast underwater plumes of oil, one 10 miles (16km) long and a mile wide.
It is thought that BP's 6in-wide (15cm) tube and stopper could capture more than three-quarters of the leak, although a smaller spill nearby also has to be contained.
The tool became dislodged from the broken well riser after it was first inserted a mile beneath the surface on Saturday night.
But it was now back in place, senior executive vice-president Mr Wells said on Sunday at the firm's US headquarters in Houston, Texas.
Over the next few days the company planned to slowly increase the amount of oil and gas flowing through the pipe to the tanker, he said.
The energy giant also suggested it had already made clear its position on paying damages for the disaster, a day after the US government demanded immediate clarification on the issue.
The Obama administration said in a letter it wanted to be sure BP would honour commitments not to limit costs to a US statutory cap of $75m (£50m).
BP said last week the cap was irrelevant and it would settle all legitimate damages claims.
"What they are requesting in the letter is absolutely consistent with all our public statements on the matter," said BP spokesman David Nicholas on Sunday.
BP would not comment on scientists' discovery of several new vast plumes of oil below the ocean's surface.
Thousands of barrels of oil a day have been leaking from the seabed
Researchers from the National Institute for Undersea Science and Technology said they had detected the slicks lurking just beneath the surface of the sea and at depths of 4,000ft (1,200m).
Samantha Joye, a marine science professor at the University of Georgia, said: "It could take years, possibly decades, for the system to recover from an infusion of this quantity of oil and gas.
"We've never seen anything like this before. It's impossible to fathom the impact."
Chemical dispersants BP has been dumping underwater may be preventing the oil from rising to the top of the ocean, the scientists said.
The find suggests the scale of the potential environmental disaster is much worse than previously feared since the Deepwater Horizon drilling rig blew up on 20 April, killing 11 workers.
Some scientists cast doubt on BP's estimate of the oil flow rate, saying the widely repeated figure of 5,000 barrels per day dramatically understates the real amount.
A week ago, BP tried to cap the well with a 100-tonne box, but gave up after it became encrusted with ice crystals.
Mississippi has become the third US state to have traces of oil wash up on its coast, along with Louisiana and Alabama.
The spill is threatening to eclipse the 1989 Exxon Valdez leak off Alaska as America's worst environmental disaster.