Wisner land field inspector Forrest Travirca, III smells a pinch of sand taken from the beach near the surf Tuesday, September 14, 2010. The beach may appear devoid of oil, but scratching the surface reveals oil just below the top layer of sand. John McCusker, The Times-Picayune

By Chris Baltimore; editing by Mohammad Zargham
Tue Sep 21, 2010 5:17pm EDT HOUSTON (Reuters) – The government is unable to confirm reports of a miles-long plume of oil lurking beneath the surface of the Gulf of Mexico from BP Plc’s giant oil spill, a government scientist said on Tuesday. The government confirmed on Sunday that BP had permanently “killed” its deep-sea well that ruptured in April and unleashed the worst spill in U.S. history. Some private scientists and academic groups say sizable amounts of oil remain trapped deep beneath the ocean surface, after a government report in August found that more than half of the 4 million barrels spewed by the well had dissipated, and much of the rest had been neutralized by natural processes. Undersea monitoring by the National Oceanic and Atmospheric Administration failed to detect significant concentrations of oil, NOAA scientist Sam Walker said. “We are continuing to find lower and lower concentrations,” Walker told reporters on a conference call. In recent weeks, U.S. monitoring vessels have seen “very clear trends of diminished concentration,” with oil detected beneath the surface in the “parts per billion” level, “which is not actionable,” Walker said. …

U.S. government: No sign of undersea plume from BP spill