The Coast Guard, BP, and the National Oceanic and Atmospheric Administration worked to assess sheen observed in the Gulf of Mexico in late September. The Coast Guard said it was able to confirm the sheen was from the well that failed in 2010.
"The exact source of the sheen is uncertain at this time but could be residual oil associated with wreckage and/or debris left on the seabed from the Deepwater Horizon incident in 2010," a Coast Guard statement read.
BP in mid-September said it confirmed that residual oil from the 2010 oil spill in the Gulf of Mexico was pushed onshore by Hurricane Isaac, which hit the southern U.S. coast in late August.
Mike Utsler, president of BP's Gulf Coast Restoration Organization, said at the time that finding oil onshore from the failed Macondo well in the Gulf of Mexico wasn't a surprise.
Oil, he said, was discovered in "isolated stretches" of beach the company was cleaning before the storm hit.
The 2010 spill in the Gulf of Mexico was the worst accidental offshore release in history.