The incident took place in Shil Dhaigar locality around 6.30 pm following which firemen rushed to the spot with a medical team and began rescue operation.
According to Deputy Collector Manoj Gohad, two bodies have been extricated so far and several inmates are trapped in the debris.
The unauthorised building was occupied at least up to the fourth floor and many are feared dead in the mishap, he said.
Municipal Commissioner R A Rajeev and District Collector P Velarasu are supervising the relief operations.