Part of the Druzhba oil pipeline that links Russia and Germany was shut down after the discovery of a leak in western Poland, the Polish pipeline operator PERNsaid Sunday, adding that supplies continued unaffected.

A leak in Poland’s Druzhba pipeline highlights Europe’s ongoing struggle to reduce dependence on Russian oil while maintaining energy security.

Poland is checking whether the Druzhba pipeline transporting oil to German refineries is leaking, according to firefighters in the eastern European nation.

Supply to customers was not affected by a leak on one of the branching pipes of the Russian Druzhba pipeline in Poland, the Polish operator Pern said in a statement on Dec. 1.

An oil spill has been detected on the northern side of the Druzhba pipeline in Poland. The NATO nation's authorities are investigating the cause of the oil spill and have temporarily shut down the Russian pipeline.