Meanwhile, scientists said they were concerned about the ooze reaching a major ocean current that could carry it through the Florida Keys.
BP PLC chief operating officer Doug Suttles said at a press conference that the company will never again try to produce oil from the well, though BP did not rule out drilling elsewhere in the reservoir.
"The right thing to do is permanently plug this well, and that's what we will do," Suttles said.
BP's mile-long tube is funneling a little more than 42,000 gallons of crude a day from the well into a tanker ship.
Special Section: Disaster in the Gulf
Were Oil Rig Warnings Ignored?
Oil Spill by the Numbers
That would be about a fifth of the 210,000 gallons the company and the U.S. Coast Guard have estimated are gushing out each day, though scientists who have studied video of the leak say it could be much bigger and even BP acknowledges there's no way to know for sure how much oil there is.
Suttles said BP would be pleased if the siphoning eventually captures half of the oil, though the company originally said it hoped the tube would catch most of it. Chemicals were also being used to disperse the oil underwater.
In the nearly a month since the oil rig Deepwater Horizon exploded off the coast of Louisiana, killing 11 workers, BP has made several failed attempts to stop the leak, trying in vain to activate emergency valves and lowering a 100-ton container that got clogged with icy crystals.
The from the spill continues. Congress is holding hearings, and the federal Minerals Management Service said Monday that Chris Oynes, who oversees offshore drilling programs, will retire at the end of the month. Oynes has come under criticism for being too close to the industry the agency oversees. His departure comes as President Barack Obama has vowed to end a "cozy relationship" between the MMS and the oil industry.
Millions of gallons of oil have already gushed into the Gulf, and researchers said that in recent days they have discovered miles-long underwater plumes of oil that could poison and suffocate sea life across the food chain, with damage that could endure for a decade or more.
The National Oceanic and Atmospheric Administration said Monday that the researchers' announcement of the oil plumes was premature, and that further tests need to be conducted to confirm that the plumes detected were indeed caused by the well blowout.
But Samantha Joye, a professor of marine sciences at the University of Georgia, said researchers have found more underwater plumes of oil than they can count from the well.
"The discovery of these plumes argues that a lot more oil and gas is coming out of that well every day, and I think everybody has gotten that fact except BP," she said.
Out in the Gulf of Mexico, the oil is mixing with a vast amount of water, but what isn't seen is the strong underwater currents that act like high-speed trains, reports CBS News correspondent Kelly Cobiella. The concern is that the oil will get swept up in one of these currents and carried east.
Engineers finally got the siphoning contraption working Sunday after several setbacks. BP PLC engineers remotely guiding robot submersibles had worked since Friday to place the tube into a 21-inch pipe nearly a mile below the sea.
Once the oil reaches the tanker, the oil is being separated from the natural gas and sea water. The natural gas is being burned off, while the crude is being sent to oil terminals.
Crews will increase how much the tube is collecting over the next few days. They need to move slowly because they don't want too much frigid seawater entering the pipe, where it could combine with gases to form the same ice-like crystals that doomed the previous containment effort. BP said it is building a second tube system as a back up.
The company said Monday that it has started drilling a second well to relieve pressure on the blown-out well and also getting ready to try a procedure known as a top-kill that uses a tube to shoot mud and concrete directly into a device on the well called the blowout preventer to stop the oil.
As engineers worked to get a better handle on the spill, a researcher told The Associated Press that computer models show the oil may have already seeped into a powerful water stream known as the loop current, which could propel it into the Atlantic Ocean. A boat is being sent later this week to collect samples and learn more.
"This can't be passed off as 'it's not going to be a problem,"' said William Hogarth, dean of the University of South Florida's College of Marine Science. "This is a very sensitive area. We are concerned with what happens in the Florida Keys."
Coast Guard Rear Adm. Mary Landry said Monday no oil has reached the loop current.