HOUSTON (Reuters) - An oil spill from a leaking underwater well grew to cover 1,900 square miles of the Gulf of Mexico on Monday as the U.S. Coast Guard scrambled to keep the slick from reaching the fragile Gulf Coast shoreline.
The well, 5,000 feet under the ocean surface off Louisiana's coast, is leaking about 1,000 barrels of oil a day. The spill, which the U.S. Coast Guard has called "very serious," has put the coasts of Louisiana, Texas, Mississippi and Florida on alert for potential oil contamination.
Swiss-based Transocean Ltd's Deepwater Horizon sank on April 22, two days after it exploded and caught fire while finishing a well for BP Plc about 40 miles southeast of the mouth of the Mississippi River.
As of Monday afternoon, there were no impacts to the shore and the spill remained about 30 miles off the Louisiana coast at least three days from landfall, said Coast Guard Rear Admiral Mary Landry.
Wildlife impact was said to be minimal. An aircrew from the U.S. Fish and Wildlife Service on Sunday spotted three sperm whales near the spill but they did not appear affected, officials said.
The incident casts a pall over the oil industry's push for access to more offshore acreage in Alaska, the Gulf of Mexico and along the East Coast, and comes just weeks after President Barack Obama unveiled plans for a limited expansion of U.S. offshore oil and gas drilling.
In an attempt at a quick fix, U.S. agencies this weekend deployed four remotely operated underwater vehicles to dive unmanned to the ocean floor to try to activate a balky blowout preventer, a 450-ton tangle of pipes and valves that usually works automatically.
If that plan fails, London-based BP, which owns the oil well and is financially responsible for the cleanup, will have to drill one or more relief wells into the damaged well bore under the seabed to intercept the flow.
The drilling effort could take several months, and BP is pursuing an interim plan to build as many as two dome-shaped covers to place over the well that could capture oil and pipe it to the surface before it can add to the spill. That could be done in two to four weeks, officials estimated.
"This is state-of-the-art technology," said Doug Suttles, chief operating officer of BP's exploration and production unit. Such containment and removal systems have been used in shallower waters but never at such depths.
Eleven workers from the rig are missing and presumed dead in what is the worst oil rig disaster in almost a decade. The Coast Guard on Friday suspended a search for the workers.
The spill is not comparable with the infamous Exxon Valdez disaster, which spilled about 11 million gallons (50 million liters) of oil into the Prince William Sound in Alaska when it ran aground in 1989. BP's well is spewing about 42,000 gallons (190,900 liters) of oil a day into the ocean, the Coast Guard estimates.
Tony Hayward, chief executive of London-based BP -- which is financially responsible for the clean-up -- traveled to the area over the weekend to oversee operations and meet with the governors of Texas, Louisiana and Mississippi.
Stormy weather over the weekend hampered cleanup efforts for BP, which has deployed an armada of ships and aircraft to contain the oil slick. In a statement, Hayward on Monday said BP was accelerating cleanup as the weather improved.
"The improved weather has created better conditions for our response," Hayward said. "This, combined with the light, thin oil we are dealing with has further increased our confidence that we can tackle this spill offshore."
BP's shares fell 2 percent on Monday on fears that the spill could lead to a big financial hit. BP has not given a detailed accounting of spending or potential liability to date.
Transocean's Chief Executive Steven Newman also traveled from Switzerland to Louisiana to support the effort.
Transocean said its insurance covers the total loss of the Deepwater Horizon and wreck removal, and that the rig has an insured value of $560 million.
The explosion occurred as the rig was capping a discovery well pending production, company officials said. Some 115 of the 126 workers on board at the time of the explosion were rescued.