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

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.

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.

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