VIENNA - The International Atomic Energy Agency (IAEA) said late Monday that its experts visited a damaged cooling tower of the Zaporizhzhia nuclear power plant (ZNPP) earlier that day but have not been able to determine the cause of a fire there on Sunday.

Russia and Ukraine have blamed each other for the incident. Russia accused Ukraine of a drone attack, while Ukraine said Russian "negligence" or arson could have sparked the fire.

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The IAEA said in a statement late Monday night that its experts stationed at ZNPP, following their observations at the site of the damaged cooling tower, assessed that "it was unlikely that the primary source of the fire began at the base of the cooling tower."

According to the statement, the experts "determined that the damage was most likely concentrated on the interior of the tower at the water nozzle distribution level, located at roughly 10 meters high," but they have not been granted access to the level.

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The IAEA expert team did not observe tire or drone remains during their inspection, and they confirmed that "there were no significant signs of disturbance of the debris, ash or soot located at the base of the cooling tower."

"The team has not been able to draw definitive conclusions on the basis of the findings and observations so far," the IAEA said in the statement, adding that it will continue further analysis.

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The United Nations nuclear watchdog said that the nuclear safety of ZNPP has not been affected by the incident as its cooling towers are not in operation. The agency also confirmed no signs of elevated radiation levels in the area of the plant's cooling towers.