The external power supply to the Russian-occupied Zaporizhzhia nuclear plant was restored on Sunday, Ukraine’s state nuclear company Energoatom and the U.N.’s nuclear watchdog said.

The plant, which is in cold shutdown, lost its last remaining power line early on Saturday due to shelling, and had to use back-up diesel generators for its own needs, such as cooling the reactor blocks.

“After almost two days of operating the emergency cooling pumps of the active zones of the reactors with power from diesel generators, the operational staff are restoring the normal regimen of powering the plant’s own needs from the energy system of Ukraine,” Energoatom said on Telegram.

Rafael Grossi, the chief of the International Atomic Energy Agency, which has two observers at the plant, confirmed the power supply had been restored.

“Our team at #Zaporizhzhya confirms the offsite power line lost yday was restored & #ZNPP is reconnected to the grid — a temporary relief in a still untenable situation,” Grossi said on Twitter, repeating his call for a protection zone around the plant.’

Russian forces occupied the plant soon after they invaded Ukraine in February, but Ukrainian operators have remained on site.

Moscow and Kyiv have blamed each other for shelling at the site of Europe’s biggest nuclear plant that has damaged buildings and raised concern about a potential nuclear disaster.