WARSAW, Poland (AP) — An oil leak was detected on a pipeline in Poland that's the main route through which Russian crude reaches Germany, the pipeline's Polish operator said Wednesday.

The operator, PERN, said it detected a leak in the Druzhba pipeline on Tuesday evening 70 kilometers (45 miles) from the central Polish city of Plock. It said the cause of the leak wasn't known.

The incident follows leaks late last month in the Nord Stream 1 and 2 gas pipelines running along the Baltic seabed, and amid an energy standoff between Russia and the West over Russia's invasion of Ukraine. Denmark and Sweden say those natural gas pipelines were attacked with large amounts of explosives.

The Druzhba pipeline, which in Russian means “Friendship,” is one of the world’s longest oil pipelines. After leaving Russia, it branches out to bring crude to points including Belarus, Ukraine, Poland, Hungary, Austria and Germany.

A Polish government security official, Stanislaw Zaryn, said the leak could be the result of an accident, but that officials were still investigating and were looking at all possible explanations.

“Different scenarios are possible. We don’t exclude any of them,” he told The Associated Press.

Firefighters were working in cornfields near the village of Zurawice to determine the exact point of the leak, according to a spokesman for firefighters, Brig. Karol Kierzkowski. He told the state news broadcaster TVP Info that approximately 400 cubic meters of spilled crude had been pumped out, and transmission along the line had been blocked off.

Germany’s Economy Ministry said that Berlin’s supplies are currently secure, with two German refineries continuing to receive supplies via the Druzhba pipeline. It said reserves at those two refineries have been increased in recent weeks, and that both can, if needed, be supplied via the German port of Rostock and the Polish port of Gdansk.

Last year, Russia accounted for around 35% of Germany’s crude oil supply. But that proportion has been reduced following Moscow's invasion of Ukraine in February. Germany's focus now is on phasing out the remaining supplies before a European Union embargo on most Russian imports goes into effect. An European Union embargo on most Russia oil goes into effect on Dec. 5.

A month ago, the German government took control of three refineries owned by Russian energy company Rosneft, which account for about 12% of Germany’s oil refining capacity.

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