The U.S. Coast Guard during the weekend responded to reports of possible oil pollution stretching into the Gulf of Mexico.
Analyzed samples from the suspected sheen contained trace amounts of petroleum hydrocarbons, oil and grease, the Coast Guard said. The dark substance is believed to be the result of an increase in sediment that was agitated by dredging operations in the Mississippi River.
Additionally, the Coast Guard said it received notifications of possible pollution in coastal areas along the Gulf of Mexico.
"Samples have been taken from the shoreline impacts for testing but the oily substance is not, at this time, suspected to be residual oil from the Deepwater Horizon oil spill," the Coast Guard said.
The Deepwater Horizon oil platform caught fire and sank in the Gulf of Mexico in April, resulting in one of the worst oil spills in the history of the industry.
The Coast Guard said it deployed containment boom to the area as a precaution.