Russian forces blindfolded and detained the head of Europe the largest nuclear power plantUkraine’s nuclear power supplier said on Saturday, reviving alarming fears about nuclear power plant safety.

Friday’s alleged kidnapping appears to have come shortly after Russian President Vladimir Putin escalated his war in Ukraine and pushed it into a new, dangerous phase by joining four Ukrainian regions that Moscow fully or partially controls and increases the threats of nuclear power.

In a possible attempt to strengthen Moscow’s control over the recently annexed territory, Russian troops captured the general director of the Zaporizhzhya nuclear power plant Ihor Murashov around 4 p.m. Friday, Ukrainian state nuclear company Energaatom said.

International Atomic Energy Agency said Saturday that Russia informed her that “the general director of the Zaporizhzhya NPP has been temporarily detained to answer questions.”

The Vienna-based IAEA said that “in accordance with its nuclear safety mandate” it was “actively seeking clarification and hopes for a swift and satisfactory resolution of this matter.”

On Friday, Putin signed agreements on the absorption of Luhansk, Donetsk, Kherson and Zaporozhye regions of Ukraine, including the territory around the nuclear power plant.

“Energaatom” stated that the Russian military stopped Murashov’s car, blindfolded him and took him to an unspecified place.

“His detention (by Russia) endangers the security of Ukraine and the largest nuclear power plant in Europe,” said the president of “Energaatom” Petro Kotin, demanding the immediate release of the director.

Russia did not immediately recognize the capture of the plant’s director.

The power plant has been used more than once caught in the crossfire war in Ukraine. Ukrainian specialists continued to operate the power plant after it was seized by Russian troops. Its last reactor was closed in September as a precaution as constant shelling nearby damaged the plant’s power lines.

The plant is a strategic trophy for Russia and has raised concerns around the world as the only nuclear plant involved in modern warfare. Active hostilities nearby mean that power is unlikely to resume anytime soon, even if Russia establishes its own governance.

It is like a separate city, where about 11 thousand people worked before the war. While many fled during the hostilities, others stayed to ensure the safety of radioactive materials and facilities.

Energoatom officials told The Associated Press on Saturday that employees of the Zaporizhzhia power plant are being forced to submit reports to Rosatom, Russia’s state-owned nuclear energy giant, which operates Russia’s nuclear power plants.

Murashov was against the transfer of the Zaporizhzhya NPP to Rosatom, but Energoatom could not confirm that this was the reason for his abduction.

Murashov had access to security codes, coordinated all work at the station, monitored the implementation of protocols and reported to Kyiv, according to representatives of “Energaatom”. Ukrainian authorities appointed him to manage the plant a few days before Russian troops entered Ukraine.

Nevertheless, “Energaatom” stated that they do not lose contact with the NPP and all important parameters of its operation are still reported to Kyiv.