United Nations inspectors are on the ground in Ukraine to survey the condition of a massive nuclear power plant that is in the middle of Russia’s war on the former Soviet state. Their presence is in response to threats of a possible nuclear disaster.

The Zaporizhzhia nuclear power station in southeastern Ukraine is the largest nuclear plant in all of Europe and provides one-fifth of the country’s electricity, according to the New York Times. Its importance to the region made it a prime target of Russia’s invading forces.

IAEA members arrived at Zaporizhzhia after shelling forced one of the reactors to shut down and led to the plant’s “complete disconnection” from the nation’s power grid for the first time in the history of the plant. The resulting blackout at the site could have caused a massive catastrophe overnight, Ukrainian President Volodymyr Zelenskyy said at the time.

Following the incident, IAEA Director General Rafael Marino Grossi went on television to say, “I think there is general recognition that we need to be there.”

“We can’t afford to lose any more time,” he said in another interview cited by the Times. “I’m determined to personally lead an IAEA mission to the plant in the next few days to help stabilize the nuclear safety and security situation there.”

Now that nuclear inspectors are on site, they are finding cause for concern. According to the experts, the station’s integrity is has been harmed.

“It is obvious that the plant and physical integrity of the plant has been violated several times,” Grossi said Thursday after the first day’s inspection.

Ukraine now is accusing Moscow of using Zaporizhzhia effectively as a military base. Which, they say, puts everyone in jeopardy.

Experts have said that despite concerns about a potential Chernobyl-style disaster, something of that scale is unlikely. Nuclear reactors are significantly stronger in 2022 than they were in the 1980s.