The chief of the International Atomic Energy Agency (IAEA) has warned that the situation at Ukraine’s Zaporizhzhia nuclear power plant is deteriorating rapidly and is “very alarming.”

The comments from IAEA director Rafael Mariano Grossi come after the facility was hit by shelling on August 5th that resulted in several large explosions near the nitrogen-oxygen station and electrical switchboard. Following this, the IAEA director called on Russia and Ukraine to provide access to the facility. So far, Ukraine has refused to grant the IAEA access, saying, “The visit to the plant will only become possible when Ukraine takes back control of the site. We consider an attempt to gain access to the Zaporizhzhia power plant would legitimize the presence of the occupiers and approve their actions.”

Russian troops have been in control of the facility since march, with reports estimating that roughly 500 soldiers and heavy equipment (including tanks) are at the facility. Ukrainian staff still controls day-to-day operations even with the Russian occupation. Ukraine has previously accused Russian soldiers of forcing facility workers to stay on-site and work, adding that they are being held at gunpoint. Russia has denied the claims, calling them “propaganda.”