Nearly 88,200 gallons of oil leaked from a Shell flow line into the Gulf of Mexico about 90 miles off the coast of Louisiana.
The leak has been secured and cleanup crews will be dispached, said Chief Petty Officer Bobby Nash.
Officials were investigating the cause of the leak, but Shell spokeswoman Kimberly Windon said the likely cause is a release of oil from the subsea infrastructure.
The Bureau of Safety and Environmental Enforcement said there have been no reports of injuries.
Officials said Shell reported the spill and had shut the wells flowing into the line.
"We are working with the United States Coast Guard and the National Oceanic Atmospheric Association to define the best approach to contain and clean up the sheen," said Windon.