The 10-mile oil sheen spotted in the Gulf of Mexico did not originate from Royal Dutch Shell's operations in the area, said the company in a statement on Thursday, according to Bloomberg.
The oil sheen, spotted on Wednesday, was estimated in size to be the equivalent of six barrels of oil.
In Shell's statement, it said its operations in the Gulf were "normal with no sign of leaks" and there were "no well control issues associated with our drilling operations in the area," according to CNN.
The US Coast Guard and oil company experts searched for the source of the sheen on Thursday, using aircrafts and undersea probes, according to AFP.
The oil slick is located 130 miles south-east of New Orleans, according to Coast Guard spokeswoman Elizabeth Bordelon. She said, "At first light this morning Air Station New Orleans sent out a ... helicopter with a pollution investigator aboard to do an overflight."
Workers for the Bureau of Safety and Environmental Enforcement were the first to notice the slick, located between two offshore oil rigs owned by Shell.
The bureau directed Shell to conduct a seafloor assessment with a robot vehicle and also told pipeline operators in the area to survey their lines, according to the Associated Press.
Natural seepage from undersea oil wells is known to occur in the area, according to the AP.
The spill was spotted on the two year anniversary of the disastrous BP oil spill that also happened in the Gulf of Mexico in April 2010, when the Deepwater Horizon rig exploded, killing 11 workers and causing severe damage to the economy and environment.