Ukraine’s national nuclear company Energoatom warned on Monday that there was a risk of rising radiation levels around the decommissioned Chernobyl nuclear power plant because the monitoring and fire-fighting system was not working, Reuters reports.

The plant where the world’s worst nuclear accident occurred in 1986 was occupied almost a month ago by Russian forces, shortly after the start of the invasion of Ukraine.

Energoatom points out that as a result, the level of radiation is no longer monitored within a radius of 30 km, the so-called exclusion zone. “There are no data on the current state of radiation pollution in the exclusion zone, which makes it impossible to respond adequately to threats,” the agency said.

According to Energoatom, seasonal forest fires, which occur mainly in spring and summer, pose a special threat because firefighters in the area cannot intervene, according to Agerpres.

“Radiation levels in the exclusion zone and beyond, not only in Ukraine but also in other countries, could worsen significantly,” warn Ukrainian experts.

Despite the presence of the Russian military, Ukrainian Chernobyl personnel continued their work on the radioactive waste facilities, although the exchange of shifts was no longer possible and there were fears of depletion of the remaining posts. On Sunday, the International Atomic Energy Agency announced that half of the Chernobyl shift personnel had been replaced by new staff.