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. The communist-era-built Druzhba pipeline was used to transport oil from Russia to Europe through its two main branches,

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

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