The Justice Department said Tuesday that it would open a criminal and civil investigation into the Gulf oil disaster as government projections showed the massive slick moving closer to shore.
After a tour of the afflicted areas, Attorney General Eric Holder said that the wide-ranging inquiry was "our obligation under the law."
Holder declined to specify whether the probe would target energy company BP, which operated the oil rig that caused the leak. However, BP shares lost 15 percent of their value as officials said the spill -- and BP's liability for economic and environmental damages -- might not be resolved for months following several failed attempts to cap the gusher.
Justice Department spokesman Andrew Ames said the inquiry would involve "all possible violations of the law," including breaches of the Clean Water, Oil Pollution and Endangered Species acts.
Holder's trip to the Gulf Coast included meetings with federal prosecutors and state attorneys general from Louisiana, Alabama and Mississippi. President Obama also told members of an independent investigating commission that laws would be changed if necessary to prevent such spills.
The Coast Guard said it was "aggressively increasing" surveillance and cleanup after the latest forecasts indicated winds pushing the oil closer to the Louisiana, Alabama and Mississippi coasts. Two Navy skimmers are on their way to join three already in place off of Mississippi's Petit Bois Island, where oil was spotted Tuesday, said the Coast Guard's P.J. Capelotti.
Asked whether this week could see some of the heaviest onshore oil contamination since the leak began six weeks ago, Capelotti said, "That's what we're gearing up for."
The government widened the fishing ban, putting nearly a third of federal Gulf waters off-limits.
BP is attempting to slow the leak, which has already surpassed the 1989 Exxon Valdez spill as the worst oil disaster in U.S. history, by positioning a cap over the opening. Coast Guard Adm. Thad Allen said the "ultimate solution" is not likely until August when a relief well can be put in place.
"They seem to be throwing up their hands," said Carl Safina, an ecologist and founder of the Blue Ocean Institute, an environmental group. "It seems like we're ruining the Gulf of Mexico, and there's nothing effective that can be done to stop it."