WASHINGTON -- Scientists heaped more criticism Thursday on the Obama administration's claim that most of the Gulf of Mexico oil spill is gone, saying that it was too early to determine the remaining oil's impact on the waters or marine life.

Most of the 4.1 million barrels of spilled oil remains in the environment even if it's not visible, posing unknown consequences for sea life and the thousands of Gulf residents whose livelihoods depend on fishing, scientists said. The scientists accused the Obama administration of painting a rosy picture while revealing only a portion of the data on which government experts based their analysis, released two weeks ago.

The testimony came as a new independent study, published in the journal Science, reported that a vast fog of oil -- 22 miles long and more than a mile wide -- is floating far below the Gulf's surface, where low water temperatures are slowing its natural breakdown.

It was the most conclusive evidence yet of a subsea oil "plume" that could linger for years, said Richard Camilli of the Woods Hole Oceanographic Institution in Massachusetts, lead author of the report.

While scientists don't know the long-term impact of that much oil floating below the water's surface, they urged the Obama administration not to make it seem that the worst of the spill is over.

"We understand that the government wants to turn a corner and wants to signal that the Gulf is on the road to recovery," Lisa Suatoni, a senior scientist with the oceans program of the Natural Resources Defense Council, an environmental group, told a congressional panel Thursday. "However, the facts simply do not bear that out. There is still a huge amount of oil in the environment."

The government's report, produced by senior officials from the National Oceanic and Atmospheric Administration and the U.S. Geological Survey, claimed that at least half of the oil that spilled from BP's Deepwater Horizon rig was gone from the environment and much of the remainder is degrading rapidly underwater.

Researchers from the University of Georgia reported that 70 to 79 percent of the spilled oil remained in the water, and that far less oil had evaporated than the government claimed.