The U.S. Coast Guard said Monday that an estimated 1.1 million gallons of crude oil has leaked into the Gulf of Mexico near a pipeline off the coast of Louisiana. Officials are concerned about the oil’s potential impact on endangered and threatened species.

The Coast Guard first reported seeing the spill on Friday, saying that an aircrew had identified the leak. In their last update on Tuesday, officials said the leak is near the 67-mile-long Main Pass Oil Gathering company’s pipeline system near Louisiana’s Plaquemines Parish. It was not specified when the leak began, but officials said the pipeline was closed down at 6:30 a.m. on Thursday.

“The volume of discharged oil is currently unknown,” officials said Tuesday. “…Initial engineering calculations indicate potential volume of crude oil that could have been released from the affected pipeline is 1.1 million gallons.”