In a statement Monday, the agency also said there are no longer firefighters available in the region to protect forests tainted by decades of radioactivity as the weather warms. The plant was seized by Russian forces on Feb. 24.

According to Monday's statement, the combination of risks could mean a ``significant deterioration'' of the ability to control the spread of radiation not just in Ukraine but beyond the country's borders in weeks and months to come.

Management of the Chernobyl plant said Sunday that 50 staff members who had been working nonstop since the Russian takeover have been rotated out and replaced