BP said it increased the amount of oil being captured from its leaking well in the Gulf of Mexico to 10,500 barrels yesterday and expects to increase that quantity in the next few days.

The well is estimated by government scientists to be gushing 12,000 to 19,000 barrels a day into the Gulf. BP said yesterday it collected 6,077 barrels in the previous 24-hour period ending at midnight June 4. The spill is the worst oil spill in U.S. history.

A “cap” over the well is capturing “probably the vast majority” of the leaking oil, Chief Executive Officer Tony Hayward told the Broadcasting Corp. today in an interview in London. BP has “a further containment system to implement this week,” he said, adding that a permanent and hurricane-proof mechanism will be in place by the end of the month.

Oil from the gushing well will remain in the water into the fall, U.S. Coast Guard Admiral Thad Allen said today on CBS’s “Face the Nation” broadcast.

“There will be oil out there for months to come,” Allen said. “This spill is holding everyone hostage. This is a siege. It’s going to go on for a long time.”

After the cap was put in place the night of June 3, gas reached a surface ship at about 11 p.m. local time, and oil was being piped to the ship about 10 minutes later, BP said yesterday on its website.

“Improvement in oil collection is expected,” the London- based company said today on its website.

“We’re hoping to improve it over the next few days,” BP spokesman Mark Salt said in a telephone interview today.

Allen said yesterday in a news conference that four vents on the cap remained open, allowing oil to flow through the cap and into the ocean. BP will try to close the vents when pressure is stabilized, he said.

The system can capture as much as 15,000 barrels a day, and BP will push toward that limit, according to Allen.

“I’d like to see us capture 90-plus percent of this flow,” Doug Suttles, BP’s chief operating officer for exploration and production, said June 4 on CBS’s “Early Show.” “That’s possible with this design.”

The shears used to prepare the well for the cap created a cut that was more jagged than had been hoped for, so there is isn’t a perfect seal between the cap and the well, Allen said. The company won’t know how bad the leakage is until it is capturing more oil, he said.

(Read More: Bloomberg News)