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Two new scientific reports raise fresh fears about the environmental fallout from the world's worst offshore oil spill.
The reports call into question government assurances that most of the oil from the ruptured well in the Gulf of Mexico is already gone.
In one of the reports, researchers determined that about three-quarters of the oil from BP's blown-out well is still lurking below the surface of the Gulf and may pose a threat to the ecosystem.
It says up to 79 percent of the 4.1 million barrels of oil were not captured directly at the wellhead.
Another report says experiments in the northeastern Gulf where so-called plumes or barely visible clouds of oil had been found earlier had turned up oil in the sediment of an underwater canyon.