BP Plc said on Tuesday that its oil-capture systems at the leak in the Gulf of Mexico collected or burned off 24,980 barrels of oil on Monday.

BP spokesman Mark Proegler said preparations continue for hooking up a third vessel, the Helix Producer, to increase oil-capture capacity to 53,000 barrels a day from the current 28,000. Proegler said BP hopes to hook up that vessel by the end of the week.

The vessel is at the leak site, but rough seas prompted BP to back off of the target hookup date of July 7 and announce Monday that the company anticipated the new system would likely start up toward the end of the week, Proegler said.

He said on Tuesday that 4- to 6-foot-high (1.3 to 2-meter) waves prompted the delay.

Of the current oil-siphoning systems, one channels oil from a containment cap atop failed blowout preventer equipment through a fixed pipe to a drillship. The other siphons oil from the blowout preventer through a hose and pipe to a rig.

An undetermined amount of oil continues to billow out from under the cap and through vents on top into the sea. A team of U.S. scientists estimate the leak gushes up to 60,000 barrels daily.

The Helix Producer will be the first step toward a new overall system, to be in place this month, involving four vessels that can all disconnect and move quickly if a hurricane approaches, BP and the Coast Guard said. They said the four-vessel system will be able to handle up to 80,000 barrels a day of crude.

Meanwhile, BP continues to make progress on a pair of relief wells intended to intercept the bottom of the blown-out well and plug the leak, the company said.

The first of the relief wells was less than 300 feet from the bottom of the leaking well that is 13,000 feet (2.4 miles) beneath the seabed, BP said. Drilling remains slow as the company often stops to use sensors to ensure the relief well is on the right path, BP said.

(Reporting by Kristen Hays; Editing by Jerry Norton)