About 88,200 gallons of oil have leaked from a Shell flow line into the Gulf of Mexico about 90 miles off the coast of Louisiana, the U.S. Coast Guard said.

Chief Petty Officer Bobby Nash said the leak has been secured and cleanup crews will be dispatched. The leak was reported Thursday.

Shell spokeswoman Kimberly Windon, in a statement late Thursday, said a helicopter saw an oil sheen near the Glider subsea tieback system at Shell's Brutus platform shortly before 8 a.m.

"There are no drilling activities at Brutus, and this is not a well control incident," Windon said.

Officials were investigating the cause of the leak, but Windon said the likely cause is a release of oil from the subsea infrastructure. Officials said the oil apparently leaked from a line connecting four wells in the Green Canyon area of the Gulf to the platform and has left a miles-long sheen.

The Bureau of Safety and Environmental Enforcement said there have been no reports of injuries.

Officials said Shell Offshore Inc. reported the spill and also said it 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," Windon said.