Scientists in the United States say much more of the oil spilt in the Gulf of Mexico could still be in the ecosystem than government figures have indicated.
A study by the University of Georgia suggests up to 79% of an estimated four million barrels of oil that leaked from the BP well is still in the Gulf.
This contrasts with official estimates by the US National Incident Command that only 25% remains.
One of the scientists, Charles Hopkinson, says the official figures are misleading.
"There is a huge difference between being dispersed and being gone. It does seem as if there have been some misinterpretations of the NIC report - claims that 50 to 75 percent of the oil being gone.
"The big picture is that there's a lot of oil that is still out there and has not gone away, so to speak."
Oil leaked into the Gulf from 20 April when the Deepwater Horizon rig explosion killed 11 workers. The flow was stopped on 15 July.