The U.S. Department of Transportation on Monday announced a civil penalty against a pipeline company for a massive 2023 oil spill into the Gulf of Mexico.

Transportation officials claimed that the proposed $9,622,054 fine is the largest ever levied in a pipeline safety enforcement case. The Pipeline and Hazardous Materials Safety Administration alleged that Panther Operating Company, LLC’s violation of safety rules led to a release of 1.1 million gallons of crude oil into the Gulf in November 2023.

The release stemmed from a failure of the Main Pass Oil Gathering pipeline system, leading to an oil slick three to four miles wide from a leak about 19 miles offshore of the Mississippi River Delta, according to the National Oceanic and Atmospheric Administration.