(CNN) -- A team of researchers in the Gulf of Mexico say they found an oily layer as thick as two inches coating the sea floor in some places, and they believe it may be from the BP spill.

"I think what we're seeing is oil that was on the surface, that has sedimented down to the bottom," said Samantha Joye of the University of Georgia.

Speaking by phone from a research vessel about 30 miles southeast of the former oil well, Joye said about a dozen core samples of the seabed were taken, at distances ranging from two miles to 80 miles from the site of the BP rupture.

She described the oil as "flocculent," fluffy like fallen snow, and ranging in thickness from less than a quarter-inch to more than two inches.

In the samples that were brought up from the deep, Joye reported there were ominously few of the usual traces of life, like worms and various types of arthropods. She also speculated that fish and invertebrates that come down to the seabed to forage could be harmed by traces of the substance.

Joye emphasized that the findings were preliminary, and that only when the team was on land could they confirm whether the substance was indeed crude oil, and use "fingerprinting" to see if it had come from the BP well.

An analyst from the National Oceanic and Atmospheric Administration cautioned against jumping to conclusions before the samples are chemically analyzed.

"To find oil in the Gulf of Mexico, either in the sediments or in the water column, is not an unusual thing," said Samuel Walker, technical data manger with the agency. "There's spillage from other vessels, there's leakage from pipelines... there are a lot of natural seeps."

But Joye said explanations like natural seepage are unlikely, given that just a few months earlier, in the same area, her team found almost no evidence of oily sediment.

"It wasn't here in May, right after the spill started," she said. "This layer has developed over the past four months."

NOAA spokesman Justin Kenney said the agency welcomes the efforts of independent researchers. Incident commander Thad Allen, the government's point man on the BP oil spill, has said he is seeking a way to compile the findings of independent scientists to construct a "metaphorical MRI" showing where the oil has gone.

Government scientists have estimated that at least 200 million gallons of oil leaked from BP's damaged well, but 74 percent of it subsequently evaporated, broke up, or was skimmed or burned off.

Those estimates have been questioned by several independent researchers over the last month. But Kenney said even if the seabed sediment turns out to be BP oil, that would not contradict the government's estimate, because it could simply be part of the 26 percent of the oil estimated to remain at large.

NOAA says it is still probing the waters for residual traces and plumes.

"We see the indications of this oil still down there," said David Valentine, a researcher with the agency. "But we don't know exactly what the concentrations are, how biodegraded it is."

CNN's Ed Lavandera, Brian Todd, and Kim Segal contributed to this report.