NEW ORLEANS — The Coast Guard discovered Saturday that oil is leaking from the damaged well that fed a massive rig that exploded this week off Louisiana’s coast, while bad weather halted efforts to clean up the mess that threatens the area’s fragile marine ecosystem.

As recently as Friday, the Coast Guard said no oil appeared to be escaping from the well head on the ocean floor. Rear Adm. Mary Landry said the leak was a new discovery but could have begun when the rig sank Thursday, two days after the initial explosion.

“This is a very serious spill, absolutely,” Landry said.

Coast Guard and company officials estimate that as much as 1,000 barrels of oil is escaping each day after studying information from remotely operated vehicles and the size of the oil slick surrounding the blast site. The rainbow-colored sheen of oil stretched 20 miles by 20 miles Saturday — about 25 times larger than it appeared to be a day earlier, Landry said.

Eleven workers are still missing from the Deepwater Horizon rig that sank Thursday about 50 miles from Louisiana’s coast. They are presumed dead, and the search for them was called off Friday.

BP PLC, which leased the rig and is taking the lead in the cleanup, says it’s studying how to stop the leak.

Bad weather rolled in Friday, bringing strong wind, clouds and rain that interrupted efforts to contain the spill.

So far, crews have retrieved about 1,052 barrels of oily water, he said.

The sunken rig may have as much as 700,000 gallons of diesel on board, and an undetermined amount of oil has spilled from the rig itself.

BP, which is taking the lead in the cleanup, said it has activated an extensive oil spill response, including the remotely operated vehicles to assess the well and 32 vessels to mop up the spill. The Marine Spill Response Corp., an energy industry cleanup consortium, also brought equipment.