The blaze started on the 13th floor of the New Koila Ghat Building, an office building on the banks of the Hooghly river, around 6.30 pm (IST). The 13th floor houses the ticketing office of the Indian Railways.
State Chief Minister Mamata Banerjee who rushed to the spot around 11 pm (IST) told the media that four firefighters and two cops were among those killed in the blaze. "The seventh body is yet to be identified."
Quoting Kolkata Police officials, the CM said that two more persons "are still missing".
According to State Fire Services Minister Sujit Bose, as many as 25 fire tenders were pressed into service and it took them nearly four hours to douse the flames.
Also read: Dhaka slum fire: 150 shanties gutted in Maniknagar
"The firefighters who died were among the first to take the elevator to the 13th floor. It's strange that the firemen took the lift to the 13th floor instead of taking the staircase or using hydraulic cranes," the CM said.
The state government has announced a compensation of Rs 10 lakh each to the families of the seven victims.
"A probe has been ordered into the fire accident. We will also investigate why the firemen didn't follow the basic protocol and took the lift," the Fire Services Minister said.