An oil pipeline that runs parallel to a leaking natural gas pipeline in Alaska’s Cook Inlet has drawn the scrutiny of the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA).

PHMSA told Hilcorp Alaska LLC, owner of both pipelines, Friday it is requiring the external inspection of the 14-mile crude pipeline, which is in operation. “The investigation stems from a gas leak on Hilcorp’s parallel natural gas pipeline that was first reported by Hilcorp...on Feb. 7, 2017. That leak continues to discharge natural gas (methane) into the waters of Cook Inlet, PHMSA said.

The crude pipeline is known as the Middle Ground Shoal (MGS) Hazardous Liquid System. It transports produced liquids (oil and water) from Hilcorp’s offshore A Platform in Nikiski, AK. From the MGS onshore facility, crude oil is piped to the Tesoro Kenai Refinery.

“Hilcorp will work with PHMSA and other state and federal agencies to ensure a thorough and timely response to the concerns in the proposed order. Hilcorp continues to focus on addressing the natural gas pipeline leak and ensuring the safety of our responders in the field,” the company said in a statement.

The ongoing leak on the natural gas pipeline is located about 2.6 miles from the A Platform and about 4.6 miles from the MGS onshore facility, as measured along the pipeline alignment.

PHMSA said the leak on the natural gas pipeline is the third since June 2014. The leak in June 2014 was followed by one in August of the same year. “The previous operator determined that those leaks were caused by rocks contacting the pipeline in areas where the pipeline was not continuously supported by the seabed,” PHMSA said.