The Nord Stream 1 pipeline from Russia to Europe has reported a drop in pressure, only hours after a leak was reported in the Nord Stream 2 pipeline in the Baltic Sea off Denmark, the German economy ministry said.

“We are investigating this incident as well, together with the authorities concerned and the Federal Network Agency,” the ministry said in a statement late Monday.

“We currently do not know the reason for the drop in pressure.”

Both pipelines carry natural gas from Russia to Europe.

While the Nord Stream 2 pipeline has never operated, Nord Stream 1 had been carrying gas to Germany until earlier this month, when Russian energy giant Gazprom cut off the supply, claiming there was a need for urgent maintenance work to repair key components.

Despite not delivering gas to Europe, both pipelines have still been filled with gas, German news agency dpa reported.

Gazprom’s citing of technical problems as the reason for reducing gas flows through Nord Stream 1 have been rejected by German officials as a cover for a political power play following Russia’s invasion of Ukraine.

Gazprom started cutting supplies through Nord Stream 1 in mid-June, blaming delays to the delivery of a turbine that had been sent to Canada for repair

The Nord Stream 2 gas pipeline was already complete when German Chancellor Olaf Scholz suspended its certification on the eve of Russia’s invasion of Ukraine in February, after Russia formally recognised two Russian-backed breakaway regions in eastern Ukraine.

Germany has been heavily reliant on natural gas supplies from Russia, but since Moscow launched its war in Ukraine on February 24, Berlin has been looking for other sources of energy.

Fears of a winter shortage have eased somewhat as gas storage has progressed in recent weeks.

“We do not see any impact on the security of supply,” the economy ministry said, referring to the pressure drop in Nord Stream 1.

“Since the Russian supply stopped at the beginning of September no gas has flowed through Nord Stream 1 any more. Storage levels continue to rise steadily. They are currently at about 91%.”

On Tuesday a ceremony is being held for the inauguration of a new pipeline, Baltic Pipe, which will bring Norwegian gas through Denmark to Poland.

The Norwegian gas is intended to have an important role in replacing Russian gas.