Ukrainian officials said power has been restored to the Chernobyl nuclear power plant on Sunday, after warning of an increased risk of radiation leaking after Russian forces reportedly knocked the plant off the energy grid earlier in the week. 

Ukrainian atomic energy ministry said in an online post on Sunday that cooling systems would operate normally after relying on backup power, Reuters reported. 

Russia has seized a number of Ukrainian power plants in its invasion on its neighbor. 

Ukraine’s Zaporizhzhia nuclear power plant, one of the largest such facilities in Europe, caught fire earlier this month following a Russian attack, raising alarm across the region. 

U.S. Ambassador to the United Nations Linda Thomas-Greenfield told the U.N. Security Council earlier this month that Russia’s focus on nuclear plants could pose a problem for Ukraine.

“Nuclear facilities cannot become part of this conflict,” she warned.”Russia must halt any further use of force that might put at further risk all 15 operable reactors across Ukraine – or interfere with Ukraine’s ability to maintain the safety and security of its 37 nuclear facilities and their surrounding populations.”

At least 549 civilians in Ukraine had been killed in the invasion since March 9, and more than 2.698 million refugees have fled the country, according to the United Nations.

Ukrainian officials had warned about a potential radiation leak if a high voltage power line connected to the plant wasn’t repaired, according to Reuters. 

Russian forces took control of the Chernobyl nuclear site at the beginning of Moscow’s invasion about three weeks ago.

“It is impossible to say the Chernobyl nuclear power plant is safe after a totally pointless attack by the Russians,” President Zelensky’s adviser Mykhailo Podoliak said at the time. “This is one of the most serious threats in Europe today.”