With the failure this weekend of BP's "top kill" attempt to plug its leaking Gulf of Mexico oil well, fears are growing that the economic and environmental impact of the nearly six-week-old spill can only spread.
Here are some facts about effects of the worst ever U.S. oil spill, triggered by the April 20 explosion of the Deepwater Horizon rig:
THE SCALE OF THE CATASTROPHE
"This is probably the biggest environmental disaster we have ever faced in this country," top White House energy adviser Carol Browner said on Sunday.
"There could be oil coming up 'til August." Browner told CBS's "Face The Nation," "We are prepared for the worst."
Louisiana, the nearest state to BP's gushing undersea well that is 42 miles out in the Gulf of Mexico, has been the most impacted by the spill so far.
Louisiana Governor Bobby Jindal said this week that more than 100 miles of Louisiana's 400-mile coast had so far been impacted by the spilled oil.
State officials have reported sheets of oil soiling wetlands and seeping into marine and bird nurseries, leaving a stain of sticky crude on cane that binds the marshes together.
Billy Nungesser, president of Plaquemines Parish, saw dying cane and "no life" in parts of Pass-a-Loutre wildlife refuge.
"Oil debris", in the form of tar balls and surface "sheen", has also been reported coming ashore since the April 20 accident in outlying parts of coastal Mississippi and Alabama.
In the week of May 17, Coast Guard officials found tar balls on some beaches in the Florida Keys, raising fears that the so-called Loop Current that runs from the Gulf of Mexico through the Florida Straits may have already brought oil from the spill far to the southeast. But laboratory tests subsequently showed the tar balls were not from the BP spill.
The U.S. government has declared a "fishery disaster" in the seafood-producing states of Louisiana, Mississippi and Alabama due to the oil spill. This makes them eligible for federal funds to offset the impact on fisherman and their communities of the oil pollution in their fishing grounds.
Louisiana's $2.4 billion seafood industry supplies up to 40 percent of U.S. seafood supply and employs over 27,000 people. The state is the second-biggest U.S. seafood harvester and the top provider of shrimp, oysters, crab and crawfish.
NOAA on Friday extended the area closed to fishing in the Gulf of Mexico as a result of the spill to 25 percent of Gulf U.S. federal waters, an area covering 60,683 square miles (157,168 square km), up from 20 percent previously.
It is taking this step as a precautionary measure to ensure that seafood from the Gulf will remain safe for consumers.
NOAA points out that approximately 75 percent of Gulf federal waters are still available for fishing.
But the ban affects hundreds of thousands of commercial and recreational fishermen, hitting the livelihoods of shrimpers, oystercatchers and charter boat operators.
Oil, some of it in thick sheets, but also in the form of sheen and tar balls, has already come ashore in Louisiana wildlife reserves like the Breton National Wildlife Refuge in the offshore Breton and Chandeleur Islands, and the Pass-a-Loutre refuge further to the south.
Over the 40 days since the spill started, wildlife officials report that 491 birds, 227 turtles and 27 mammals, including dolphins, have been collected dead along the U.S. Gulf Coast, according to an update released on Sunday by the oil response unified command.
Officials stress that not all of the deaths were necessarily caused by the BP spill, and that some will have been from natural causes.
Of the 491 dead birds collected, only 28 were visibly oiled. A further 66 visibly oiled birds were rescued alive.
Journalists and scientists have also reported seeing at least one shark, and other creatures like eels and turtles, swimming through surface oil.
Wildlife officials say however they expect more marine creatures, birds and mammals will be affected.
Scientists say they are also concerned about the unseen and unknown effects on the marine environment and food chain of underwater "plumes" of dispersed oil, some of them several miles (km) long, emanating from the deepwater spill site.
Tourism operators in Louisiana, Mississippi and Alabama -- from hotel owners to restaurateurs and boat charterers -- have reported cancellations as a result of the oil spill, although some are picking up other business from journalists, officials and cleanup workers who have flocked to the Gulf Coast.
Amidst a scare involving tar balls found on Florida Keys beaches -- later declared not to have come from the BP oil spill, Florida's $60-billion-a-year tourism industry is also losing millions as a result of the incident, a top state tourism marketing official said earlier this month.
Of all the threatened states, Florida has the most to lose. Tourism is its economic lifeblood, its largest industry, generating $60 billion in spending from more than 80 million visitors a year, bringing in 21 percent of all state sales taxes and employing nearly 1 million Floridians.
Officials say even the mere threat of oil pollution from the spill is enough to make a significant "dent" in the tourism industries of Florida and other Gulf states.
Mississippi, Alabama and Florida are spending millions of dollars -- paid for by BP -- to get the message out that their beaches are, for the moment, free of oil.
Major shipping channels and ports on the U.S. Gulf Coast remain open, although some industry sources have reported possible delays caused by the oil slick.
The National Oceanic and Atmospheric Administration said on Friday it had begun work to survey a new ship anchorage site at the mouth of the Mississippi River for ships to undergo inspection and oil decontamination before entering ports.
U.S. authorities are anxious to keep Gulf shipping operating to maintain vital U.S. exports and imports. NOAA says the Lower Mississippi River ports export over 50 million metric metric tones of corn, soybeans and wheat each year, more than 55 percent of all U.S. grains inspected for shipment.
Other sources: NOAA
(Reporting by Matthew Biggin Venice, Louisiana, Steve Gorman in Los Angeles and Pascal Fletcher in Miami, Editing by Pascal Fletcher and Sandra Maler)