The Polish operator of an oil pipeline running to Germany said it has fixed the damage that caused a leak earlier this week and that the flow of crude oil from Russia has been fully restored.

The state-run operator, PERN, said that both lines of the Druzhba pipeline were operating normally, transporting oil.

It said that the cause of the leak that occurred on Tuesday in a field in central Poland is still being investigated.

The Druzhba pipeline, which in Russian means “Friendship”, was built in the 1960s and is one of the world’s largest pipeline systems, bringing crude oil from Siberia to central Europe.

It branches to reach Belarus, Ukraine, Poland, Hungary, Austria and Germany.

The leak follows attacks last month on the Baltic Sea Nord Stream 1 and 2 gas pipelines, in which explosives are said to have been used.

Europe has been taking steps to reduce its reliance on Russian energy after Russia’s invasion of Ukraine.