The partial collapse occurred in the machine hall of the same reactor that exploded in 1986 triggering the world's worst nuclear disaster, the official Russian news agency RIA Novosti reported.
No one was hurt in the latest incident and radiation in the so-called exclusion zone around the plant did not change, the power station's management said.
The Emergencies Ministry attributed the cause of the roof collapse to a buildup of snow.
The damaged area of the roof measured approximately 6,000 square feet, Pravda reported.
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