Marine scientists Thursday said an underwater plume of drifting oil from the BP Plc disaster stretched at least 35 kilometres long in the Gulf of Mexico and proved the need for rethinking clean-up operations after deepwater drilling accidents, dpa reported.
The data released by scientists from Woods Hole Oceanographic Institution and other groups would likely become a "major part of the case" that the US government is developing against parties responsible for the spill, said Steve Murawski of the National Oceanic & Atmospheric Administration (NOAA).
BP and its subcontractors have spent billions of dollars cleaning up the months-long spill from the April 20 explosion of the Deepwater Horizon drilling rig operating at 1.5 kilometres below the ocean surface.
But most of BP's clean-up efforts have been focussed on surface oil.
The study "established that oil can exist down there ... but there's no technology for clean up at this depth," Richard Camilli of Woods Hole told the German Press Agency, dpa.
The scientists discovered the plume of oil at 1.1 kilometres beneath the ocean surface in mid-June, but their work in collecting samples was cut short by the approach of Hurricane Alex.
It is not known what has happened to the plume, but the scientists intend to go back and take added measurements.