(Bloomberg) -- Ukraine and Russia are stoking fears over potential exposure to radiation at the defunct nuclear power plant in Chernobyl that Kremlin troops are now withdrawing from.

Russians who began leaving the Chernobyl nuclear plant got “significant doses” of radiation from digging trenches at the highly contaminated site, Ukraine’s state power company said Friday. Moscow’s envoy to the International Atomic Energy Agency reported Thursday that Ukraine workers at the site have sabotaged transmission lines used to monitor radiation safety. 

Neither account could be independently verified by IAEA monitors. The agency’s Director General Rafael Mariano Grossi returns to Vienna on Friday after consultations with senior nuclear officials in Ukraine and Russia. The Argentine diplomat will give a press briefing at 2:30 p.m. Vienna time.

The 2,600 square kilometer (1,000 mile) Chernobyl exclusion zone, site of the deadly 1986 meltdown, contains long-lived radioactive material that will take thousands of years to decay. It also houses a nuclear-waste facility, where spent fuel from Ukraine’s reactors is encased for safe, long-term storage. 

The more immediate radiation concerns in Ukraine are located at the country’s 15 other reactors which are operating in a warzone. Vadim Chumak, head of the external exposure dosimetry lab at Ukraine’s National Research Center for Radiation Medicine, told MIT Technology Review this week that he’s more concerned by the risk posed by Russia’s occupation of the Zaporizhzhia Nuclear Power Plant in the southeast of the country.

“In Zaporizhzhia they have six reactors, plus spent fuel storage,” he said. “If there was any damage to the spent fuel assemblies stored at Zaporizhzhia, it could result in an enormous radiological emergency, comparable to what happened in Chernobyl.”  

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