The letters were received by the chief minister's office a week ago, they said.
"The letters came after the recent anti-Naxal operations in Gadchiroli, in which 39 Maoists were killed. The letters have been handed over to the police for further investigations," the sources said.
According to the ministry sources, both letters mentioned the Gadchiroli encounters, and threatened Fadnavis and his family members.
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