TEL AVIV (MarketWatch) - A severe oil spill has followed last week's explosion and fire at an offshore Louisiana oil rig, weekend media reports said.

The April 20 explosion occurred at a Transocean Ltd. drilling rig in the Gulf of Mexico. On Friday, the Coast Guard said it had suspended its active search for 11 missing members of the crew on the rig.

Of the 126 people working on the rig, 115 were safely evacuated. Nine of those missing are employees of Transocean, RIG, -4.26% the Zug, Switzerland, offshore-drilling contractor, and two are employed by a third-party company.

The rig was doing work for BP Plc, BP, -1.18% (BP) the U.K. oil major, at the time of the explosion. BP is spearheading efforts to contain the situation, reports say.

The leaking well was discovered Saturday and the leak could have occurred when the rig sank on Thursday, media reports say. They quote a Coast Guard admiral, Mary Landry, as saying that the spill is "very serious."

Media reports cite BP and the Coast Guard as saying that as much as 1000 barrels, or 42,000 gallons, of oil is leaking each day.

The spill covers 400 square miles of the Gulf of Mexico about 40 miles offshore, reports say. Inclement weather -- winds and rain -- is hampering cleanup efforts. The Associated Press also reported that the wellhead's depth, 5,000 feet, makes stopping the leak that much more difficult.

Media reports suggest that the disaster on the rig was caused by a blowout, in which a burst of oil or gas is suddenly pushed to the surface. But a firm cause of the rig accident has not yet been announced.