Five fire tenders have been pressed into service as the fire broke out at a branch of the Syndicate Bank at a multi-storey building at around 9.40 AM, they said.
The building, which is also a residential one, was partially evacuated and a unit of disaster management team of the Kolkata police reached the spot.
The fire is yet to be fully controlled, a senior police official said.
"The cause of the fire is not known. It seems the central air conditioning system is the origin of the fire, but it's still unclear. Our first job is to douse the flame without any casualty," he said.