Poland’s PKN Orlen said that oil supplies to its Plock refinery were not interrupted as a result of a leak detected in the Druzhba pipeline.

Polish operator PERN has detected a leak in one pipeline in the Druzhba system that carries oil from Russia to Europe, it said on Wednesday.

Poland said on Wednesday it had detected a leak in one of the Druzhba pipelines bringing oil from Russia to Europe and said it was probably caused by an accident, although the event may still stoke concerns about the security of Europe’s energy supplies.

The discovery of the leak in the main route carrying oil to Germany, which operator PERN said it found, comes as Europe faces a severe energy crisis in the aftermath of Moscow’s invasion of Ukraine which has cut supplies of gas in a continuing stand-off.

PERN said in a statement that at this point the exact causes of the leak were unknown. It was detected in a section of the pipe around 70 kilometers from the central Polish city of Plock.

The Druzhba oil pipeline, whose name means “friendship” in Russian, is one of the world’s largest, supplying Russian oil to much of central Europe including Germany, Poland, Belarus, Hungary, Slovakia, the Czech Republic, and Austria.