Poland has stopped shipping oil through part of the western section of the Druzhba pipeline that sends crude to Germany after a leak was detected late Saturday, according to Polish pipeline operator PERN.

Shipments have stopped through one of the two lines, PERN said in a statement on its website, adding the cause is under investigation. It said other Druzhba assets, including the Pomeranian section that is used to pump crude oil to Germany that arrives in tankers, are operating normally.

Polish refineries are receiving crude and the situation isn’t affecting domestic drivers’ access to fuel, according to the pipeline operator.