The sheen is south and west of the Mississippi Canyon Block where the Macondo well blew up last year. That explosion killed 11 men and led to the worst oil spill in U.S. history.
There are dozens of active leases on drilling sites in the area where the new sheen has popped up. Several companies hold the leases, including BP, Chevron and Shell.
BP said it has already sent out a crew to investigate and found that the sheen was not caused by its operations.
BP spokesman Daren Beaudo said his company had sent several remotely controlled mini-submersibles into the water over the weekend to investigate.
Rick Rainey, a spokesman for the energy services firm Enterprise Products Partners L.P., said the U.S. Coast Guard had asked his company to check one of its pipelines in the Green Canyon area over the weekend because of the sheen.
"We spent the last few days inspecting our lines. Everything's fine with the line," he said. "What I understand from our guys who have heard from the Coast Guard is that the sheen has since dissipated."
The other oil companies are either still investigating or have not commented on the sheen.
The Associated Press contributed to this report.