Repairs are underway at Ukraine’s Zaporizhzhia nuclear power plant after “local ceasefire zones” were established in the area, the United Nations nuclear watchdog said on Saturday.

“Restoration of off-site power is crucial for nuclear safety and security. Both sides engaged constructively with the [International Atomic Energy Agency] to enable complex repair plan to proceed,” the IAEA wrote in a post on X.

The Russian-occupied facility in southeastern Ukraine has been cut off from the national grid for four weeks — its longest blackout since the Russia’s invasion in February 2022. The plant has been using on diesel generators since its last power line went down last month.

Without reliable power, Europe’s largest nuclear plant risks losing the cooling needed to keep its reactors stable.

“The situation is critical,” warned Ukrainian President Volodymyr Zelenskyy in late September. “The generators and the plant were not designed for this, and have never operated in this mode for so long. And we already have information that one generator has failed,” he said.

Ukraine’s Energy Ministry reportedly confirmed that specialists were proceeding on the latest round of repair works of the power lines.

“The only reason for the unprecedented risks and threat of a radiation incident in Europe is Russian military aggression, the occupation of the Ukrainian Zaporizhzhya NPP and the systematic shelling of Ukraine’s energy infrastructure,” it said in a Telegram post.