A major gas pipeline from Russia to Germany was turned off for annual maintenance on Monday, Reuters reported. According to operator data, Physical gas flows through the Nord Stream 1 pipeline from Russia to Germany plunged on Monday morning.

The Nord Stream 1 pipeline, Germany’s main source of Russian gas, is scheduled to be out of action until July 21 for routine work that the operator says includes “testing of mechanical elements and automation systems.”

However, European governments, markets and companies are worried the shutdown might be extended due to war in Ukraine.

Russia’s Gazprom last month reduced the gas flow through Nord Stream 1 by 60%. Gazprom cited technical problems involving a gas turbine powering a compressor station that partner Siemens Energy sent to Canada for maintenance and couldn’t be returned because of sanctions imposed over Russia’s invasion of Ukraine.

Canada said over the weekend that it would allow the part to be delivered to Germany.

German politicians have dismissed Russia’s technical explanation for last month’s reduction in gas flows through Nord Stream 1, saying the decision was a political gambit to sow uncertainty and push up prices.

German Vice Chancellor Robert Habeck has said he suspects that Russia may cite “some little technical detail” as a reason not to resume gas deliveries through the pipeline after maintenance, AP reported.