As recently as Friday, the Coast Guard said no oil appeared to escaping from the well head on the ocean floor. Rear Admiral Mary Landry said the leak was a new discovery but could have begun when the rig sank on 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 yesterday — 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, said it is studying how to stop the leak.

The bad weather rolled in Friday, bringing with it strong wind, clouds and rain that interrupted efforts to contain the oil spill.

“We had 8-foot seas and a storm going through, that was a reason for cause and concern,’’ said Coast Guard Petty Officer John Edwards.

He was uncertain when weather conditions would improve enough for the cleanup to resume. 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.

About a half-dozen boats were using booms to trap the thin sheen. There was no sign of wildlife being affected.

The 11 missing workers came from Texas, Louisiana, and Mississippi. Neither the Coast Guard nor their employers have released their names.

The other 115 crew members made it off the platform; two remained hospitalized.