The U.N.’s nuclear watchdog said on Monday it had found anti-personnel mines in an area of the Russian-held Zaporizhzhia nuclear power plant in Ukraine and complained for the second month running that this violated safety procedures.

The plant, Europe’s largest nuclear facility, was seized in the first days of Russia’s invasion last year. Ukraine and Russia accuse each other of shelling around the station and the International Atomic Energy Agency has been trying to set up a safety mechanism to prevent accidents.