The spill had spread to a 32 by 32 kilometre area by Saturday, from the 3 by 13 kilometre area on Friday, the Houston Chronicle reported. The rig sunk about about 84 kilometres south-east of Venice, Louisiana.

A major oil spill was looming in the Gulf of Mexico as US Coast Guard officials confirmed Saturday that the well at the site of an oil rig disaster was leaking.

Petty Officer John Edwards told CNN that 1,000 barrels of oil - about 168,000 litres - were seeping from at least two places on the floor of the Gulf under the site.

One of the leaks was at the actual well site, while a second leak was from a pipe connected to the well. The Coast Guard has been using robotic cameras to search the area and until Saturday had found no evidence of a leak.

The Deepwater Horizons rig was struck Tuesday night by an explosion, leaving it aflame until it sunk on Thursday. The cause of the explosion on the rig owned by Swiss drilling contractor Transocean Ltd had not been determined.

The search has been suspended for 11 missing crew members. Another 115 crew members were evacuated, 17 were hurt in the blast.

“Command has shifted focus over to containment and recovery operations,” Mr. Edwards said.

The rig sunk about about 84 kilometres south-east of Venice, Louisiana.

The spill had spread to a 32 by 32 kilometre area by Saturday, from the 3 by 13 kilometre area on Friday, the Houston Chronicle reported.

“This is a very serious spill,” Rear Admiral Mary Landry told reporters Saturday.

The explosion occurred as the rig was finished drilling a 6,000 - metre exploratory well for British oil giant BP. The company was scrambling to figure out how to seal the well off on the sea floor, the Chronicle reported.

Heavy weather that brought lethal tornadoes to the Gulf Coast region also stirred heavy seas that forced the oil skimming boats to retreat to shore.

The cleanup has already contained more than 132,000 litres of oily water mix from the surface. Another 2.8 million litres of diesel fuel had been stored on the rig and have not been retrieved.

The Coast Guard has warned that a larger leak of crude would pose extreme threat to the commercial and recreational fishing industry in the Gulf and to the ecologically fragile coastline of Louisiana and other nearby states.

On March 31, President Barack Obama backed new drilling for oil and natural gas off parts of the US coastline as part of the An estimated 90 rigs drilling in the Gulf of Mexico provide 1.7 million barrels of oil a day, nearly one-third of total US production.