An estimated 2,100 barrels of crude leaked from a Royal Dutch Shell facility in the Gulf of Mexico Thursday, the company and federal safety regulators said.

A Shell helicopter observed a sheen Thursday in the vicinity of four wells that sit along the seafloor in an oil field about 165 miles south-southwest of New Orleans, The Bureau of Safety and Environmental Enforcement said. The agency, which regulates offshore oil activity, said the sheen was 2 miles by 13 miles.