The huge slick from the Gulf of Mexico oil spill threatened Louisiana shores west of the Mississippi Delta on Monday as BP Plc said it was trying multiple options to control the leak, without being sure that they would work.

Fears mounted of a prolonged and growing environmental and economic disaster for the U.S. Gulf Coast after a weekend setback in an initial undersea move by the oil giant to contain the spill, which could become the worst in U.S. history.

BP Chief Operating Officer Doug Suttles said the company, facing enormous pressure from the U.S. government and public, was pursuing multiple possible technical solutions in a bid to contain its gushing seabed well and eventually plug it.

What we've been doing is pushing parallel paths because we don't know which one's going to work, he told CNN.

BP said on Monday it had incurred $350 million in costs so far from the spill, suggesting the final bill could be much higher than many analysts predicted.

Its shares fell about 1 percent, lagging a rise in the STOXX Europe 600 Oil and Gas index.

After a buildup of crystallized gas stymied an initial attempt by BP to place a large containment dome over the well leak, Suttles said the company was now considering trying to fit a smaller top hat dome over the fissure. The aim would be to then funnel the captured oil to a surface tanker.

Other options included trying to block the well's failed blowout preventer with a junk shot of rubber or other materials, or fitting a new valve or preventer. A relief well being drilled to try to finally plug the ruptured well could still take 75 to 80 days to complete.

We've brought the world's experts together to try to help us understand how do we make these successful, Suttles said on NBC's Today show. I can't tell you if any one of them will work but as long as we have options we're going to keep trying. The goal here has to be to get the flow stopped.

Forecasts showed the uncontrolled massive oil spill shifting farther west, approaching the important shipping channels and rich seafood areas off the central Louisiana coast, west of the Mississippi Delta.

RISK OF MORE OIL ONSHORE

The environmental group Greenpeace issued an unconfirmed report late on Sunday that said traces of oil had been found onshore at Port Eads, the southernmost point of Louisiana, which is accessible only by boat or helicopter.

A 24-hour forecast from the National Oceanic and Atmospheric Administration said winds could push oil ashore in the Mississippi Delta, Breton Sound, the Chandeleur Islands and areas directly north.

BP said in a statement its costs so far included spill response, containment, relief well drilling and payments to Gulf Coast states to speed their response plans.

The final bill could be much higher than many analysts predicted as at least 5,000 barrels (210,000 gallons/795,000 liters) of oil a day have been gushing unchecked into the Gulf since the Deepwater Horizon rig exploded on April 20, rupturing the well and killing 11 crew members.

The spill threatens economic and ecological disaster on Gulf Coast tourist beaches, wildlife refuges and fishing grounds across four states. It has forced President Barack Obama to rethink plans to open more waters to drilling.

The two Louisiana parishes directly west of the Mississippi delta declared states of emergency on Sunday in anticipation of a battle to keep oil from coming ashore. Additional staging areas for the spill response have been set up in that area.

Tar balls washed up on Alabama's Dauphin Island, a barrier island and popular beach resort, during the weekend and local tourism operators said vacation traffic had already slowed to a trickle because fears of the spill's impact.

Fishing is suspended in parts of the Gulf waters and much of the Louisiana coast. Many tourists have been scared away by reports of reddish, putrid water offshore, even though the coast is currently unaffected.

You wait all year for your vacation -- you don't want to spend it in what you perceive is going to be a cesspool, said Gary Bratt, owner of a company that rents beach equipment on Alabama's Dauphin Island.

CONGRESSIONAL HEARINGS

Top officials from BP and some of the other companies associated with the ruined Deepwater Horizon drilling platform are expected to get a grilling at congressional hearings on Tuesday and Wednesday.

The U.S. Coast Guard and the U.S. Minerals Management Service also plan an investigation into the drilling rig's sinking, starting in Kenner, Louisiana, on Tuesday.

Efforts to close valves on a failed blowout protector have also been scrapped. Conducting operations a mile below the ocean's surface are complicating relief efforts as engineers work with remote-controlled vehicles in the inky blackness.

Delays in getting the containment dome up and running increase the chances the leak could become the worst U.S. oil spill, surpassing the 1989 Exxon Valdez disaster in Prince William Sound, Alaska.

Rough seas threaten to curtail containment activities in the next few days, including controlled burns, the laying of boom and spreading of chemical dispersant.

The spill's major contact with the shoreline so far has been in the unpopulated Chandeleur Islands off Louisiana, which is a mostly a wildlife reserve and bird sanctuary.

(Additional reporting by Anna Driver in Houston; Tom Brown and Pascal Fletcher in Miami; Steve Gorman and Verna Gates on Dauphin Island, Alabama; Don Pessin in Venice, Louisiana; and Tom Bergin in London; Writing by Pascal Fletcher and Ros Krasny; Editing by Bill Trott)

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