NEW ORLEANS – Oil leaking from a sunken drilling rig in the Gulf of Mexico oozed slowly toward the coast Monday, endangering hundreds of miles of marshes, barrier islands and white sand beaches in four states from Louisiana to Florida.

The areas, home to dolphins, sea birds, prime fishing grounds and tourist playlands, could be fouled later this week if crews can’t cut off an estimated 42,000 gallons a day escaping two leaks in a drilling pipe about 5,000 feet below the surface.

The rig Deepwater Horizon, owned by Transocean Ltd. and operated by BP Plc., exploded April 20 and sank two days later about 40 miles off the Mississippi River delta. Eleven of the 126 workers on board at the time are missing and presumed dead; the rest escaped. The cause of the explosion has not been determined and oil has been leaking ever since.

As of Monday afternoon, it covered an area that was 48 miles long by 39 miles wide.

Crews used robot submarines to activate valves in hopes of stopping the leaks, but they may not know till Tuesday if that strategy will work. BP had also mobilized two rigs to drill a relief well if needed. Such a well could help redirect the oil, though it could also take weeks to complete, especially at that depth.

The spill, moving slowly north and spreading east and west, was about 30 miles from the Chandeleur Islands off the Louisiana coast Tuesday. The National Oceanographic and Atmospheric Administration said it would likely be several days before any oil reaches the coast.

In Louisiana, Gov. Bobby Jindal asked the Coast Guard to deploy oil containment booms in the Pass A Loutre wildlife area, a 115,000-acre preserve that is home to alligators, birds and fish near the mouth of the Mississippi River.

The Deepwater Horizon, owned by Transocean Ltd. and operated by BP Plc., was drilling about 40 miles off the delta of the Mississippi River when it exploded.