Oil from a massive spill in the Gulf of Mexico began to wash ashore along the Gulf Coast this evening after BP asked the U.S. government for help cleaning up the mess.
According to the Associated Press, faint fingers of oily sheen could be seen lapping at the Louisiana shoreline.
Earlier, BP asked the U.S. Department of Defense for advanced imaging technology and other equipment to help contain the spill, which the Obama administration labeled earlier today as an event of "national significance."
Homeland Security Secretary Janet Napolitano said during the White House briefing that designating the spill as one of "national significance" means that "we can now draw down assets from across the country" to assist with cleanup.
She said 1,100 people are working on the cleanup effort, which so far has collected 685,000 gallons of oil and water from the polluted Gulf.
Earlier this afternoon, the Coast Guard had predicted that oil could begin to hit the Louisiana coastline as early as tonight. At the time, the floating oil slick was just 3 miles from land and 25 miles from the nearest populated area.
The White House said 174,060 feet of flotation booms had been deployed to corral the floating oil. It said an additional 243,260 feet is available and 265,460 feet has been ordered.
It said 76 tugs, barges and skimmers were on scene to help in containment and cleanup, along with six fixed-wing aircraft, 11 helicopters, 10 remotely operated vehicles, and two mobile offshore drilling units.
BP's chief operating officer, Doug Suttles, said the company has been reviewing research on using chemical dispersants to break up the oil -- pumping them all the way down to the leaking wellhead to keep the crude from reaching the surface.
That's been done before, but never at such depths. The wellhead is almost a mile underwater, 50 miles south of the mouth of the Mississippi River.
U.S. Coast Guard Rear Adm. Mary Landry called it "a novel, absolutely novel idea."
At an afternoon event in the White House Rose Garden, President Obama said that the federal government is prepared to assist with cleanup efforts.
"While BP is ultimately responsible for funding the cost of response and cleanup operations, my administration will continue to use every single available resource at our disposal, including potentially the Department of Defense to address the incident," Obama said.
"I have ordered the secretaries of the Interior and Homeland Security, as well as administrator Lisa Jackson of the Environmental Protection Agency, to visit the site on Friday to ensure that BP and the entire U.S. government is doing everything possible not just to respond to this incident but also to determine its cause," the president said.
Louisiana Declares State of Emergency
Louisiana Gov. Bobby Jindal declared a state of emergency today because of the oil slick.
Meanwhile, Louisiana shrimpers filed a class-action lawsuit against BP, the owners of the oil rig, and Halliburton, which they say was working to cement the rig's well and well-cap. The suit claimed that these companies and others were negligent in allowing the explosion that led to the spill, which they claim now threatens their livelihoods. They are asking for damages of at least $5 million.
Jindal said BP had agreed to allow local fishermen to assist in the expected cleanup. Under the agreement, shrimpers and fishermen could be contracted by BP to help. Jindal said the state was also training prison inmates to help clean up wildlife harmed by oil slicks moving toward shore.
Billy Nungesser, the president of Plaquemines Parish, the county closest to the spill, said he thought BP underestimated what's about to come ashore and are only asking for help now that it may be too late.
"We know the weather's coming. We know the wind is going to be 25 to 30 knots coming, blowing that oil into the bayous," he said. "Somebody's got to be able to draw a line in the sand."
Cleanup Could Cost $8 Billion
With five times more oil leaking into the Gulf of Mexico than originally estimated and the price tag for last week's explosion predicted at $8 billion, questions about BP's response and level of responsibility are mounting.
BP's Suttles admitted some responsibility for the disaster "because we're the lease holder," but assigning blame, he said, should come after the cleanup.
"I can tell you we're not worried about that right now," he said. "Who's ultimately responsible for what will come out over time through an investigations process."
The new leak estimate is about 5,000 barrels a day, according to the National Oceanic and Atmospheric Administration. Suttles told ABC News he still believes it to be between 1,000 barrels -- the company's original estimate -- and 5,000.
The Deepwater Horizon rig was reportedly not equipped with a shutoff switch that could have been used to try to close the well. Such switches are not required in the United States, but are used in other countries such as Norway and Brazil.
But Suttles said the rig was equipped with some safety devices that should have prevented this kind of spill.
"They didn't do that, we don't know why they didn't do that and ultimately we will find out," he said.
Suttles was quick to point out that another company was operating the rig at the time of the explosion, not London-based BP.
"I can say that we had equipment required by the regulations," he said. "We don't know why, when the accident occurred, and I should probably clarify, the lease we are drilling on is owed by BP and a few other companies."
Parts of the massive spill were set on fire Wednesday as part of an experiment to try and stop the oil slick from reaching the coastline. Officials said the burn worked, but it was too windy today to try it again.
As the oil approached the coastline, biologists said it threatened as many as 400 species, including sea turtles and dolphins.
One ray of hope is that about 30 percent of an oil slick usually evaporates in the strong southern sun, and microbes and waves take care of another large portion.
"Mother nature does a much better job at cleaning up than we do of picking up," said Ed Levine, an oceanographer with the National Oceanographic and Atmospheric Administration.
Gulf of Mexico Oil Spill: Slick Close to Shore
The Deepwater Horizon drilling rig, operated by BP Oil and owned by Transocean Ltd., exploded and started burning April 20. Eleven rig workers were never found and are presumed to have died.
BP and its contractors are fighting a high-stakes battle to keep the spill from getting worse. They have tried, unsuccessfully so far, to cover the leaking wellhead with a dome or close it with a submersible robot.
Oil from the area is called light sweet crude, but Edward Overton, a professor emeritus of environmental science at Louisiana State University, said the name is deceptive. It contains heavy compounds, called asphaltenes, that do not burn easily or evaporate, even in the warm climate off Louisiana.
"When you've got a spill like this," said Overton, "there are three things you can do. You can burn it, scoop it up out of the water, or use chemical dispersants to break it up. This oil is not particularly good with any of those three."
"With light crude," he said, "you could burn most of it -- 70 or 80 percent. With heavy crude, I don't know. I'm not optimistic."
ABC News' Matt Gutman, Jake Tapper and Sam Champion provided additional information. ABC News Radio and The Associated Press contributed to this report.