Chernobyl nuclear power plant and all installations of the Chernobyl Exclusion Zone have been completely disconnected and are now without electricity, Ukraine’s state-owned energy company announced.

Russian forces attacked the former nuclear facility on the very first day of the invasion (February 24), seizing it after heavy fighting and taking its approximately 210 employees hostage, Previously reported Live Science. Now that the plant has been disconnected from the electricity grid, the approximately 20,000 units of spent nuclear fuel stored in the plant’s cooling tanks will no longer benefit from active cooling.

Ukrainian officials have warned that this could increase the likelihood of evaporation and release of nuclear material and give a dangerous dose of radioactive material to plant personnel. Some nuclear energy experts have warned, however, that as the spent fuel rods are now 22 years old and much cooler than they were, this event is unlikely.

Related: 5 weird things you didn’t know about Chernobyl

“The spent fuel rods are at least 22 years old. They have very little heat to dissipate,” Mark Nelson, chief executive of the Radiant Energy Fund, which advises businesses and nonprofits on nuclear energy, wrote on Twitter. “Their heat is low enough that the experts I spoke to expect weeks or even months to heat the water enough to dry out the pool. Even then, natural air circulation should suffice.

The Ukrainian State Service of Special Communications and Information Protection of Ukraine (SSSCIP) blamed the blackout on “occupant damage”, although there has yet to be an independent verification of the cause.

Ukrainian Foreign Minister Dmytro Kuleba said the reserve diesel generators at the Chernobyl power plant had a capacity of 48 hours, and called for a ceasefire to restore electricity.

Meanwhile, officials from the UN’s International Atomic Energy Agency (IAEA) have expressed growing concern over the well-being of Chernobyl personnel, who have been held hostage at the plant for two weeks. Workers usually left the radioactive factory after the end of working hours, but they are now forced to live on site.

Systems set up to monitor nuclear materials at the Chernobyl radioactive waste facility stopped transmitting data to the UN nuclear watchdog on Tuesday (8 March). Safeguards are the technical measures the IAEA uses to track nuclear materials and ensure that they do not fall into the wrong hands. With these offline, the agency has no way of knowing the location of the nuclear materials at the plant, increasing the possibility that they could fall into the wrong hands.

The IAEA said in a statement that “remote transmission of data from safeguards monitoring systems installed at the Chernobyl nuclear power plant had been lost” and that while workers had “limited access to food and water, and medicine”, the “situation for the staff was deteriorating.

Facility personnel are responsible for decommissioning the site and ensuring the safe disposal of radioactive materials inside the plant’s old reactors. However, since the Russian occupation of Chernobyl, this work has been suspended. Prior to the power outage, workers could only be contacted by email.

“I am deeply concerned about the difficult and stressful situation faced by personnel at the Chernobyl nuclear power plant and the potential risks this entails for nuclear safety,” IAEA Director General Rafael Grossi said in a statement. the press release. “I call on the forces effectively controlling the site to urgently facilitate the safe rotation of personnel on site.”

Eight of Ukraine’s 15 operational nuclear reactors are still online, Ukraine’s nuclear regulator said in the statement, including two at the Zaporizhzhya plant which was captured by Russian forces last week, previously reported. reported Live Science. Staff at the Zaporizhzhya plant, which briefly caught fire after being shelled during its capture, are working shifts. Radiation at both Chernobyl and Zaporizhzhya is said to be at normal levels.

Originally posted on Live Science.