The front portion of the four-storied, almost century-old building on 66, Burrtola Street within Posta police station limits, collapsed at around 2.30 pm.
"Nobody is injured in the incident but we are running a thorough search under the rubbles," a senior officer of Kolkata Police Disaster Management Group, which rushed to the spot, said.
A couple of families were staying on the rear side of the building and they are safe, he said.