As many as 300 firemen and 40 fire tenders were fighting the blaze in Stephen Court that originated from one of the lifts between the fifth and sixth floors of the building, Fire Services Minister Pratim Chatterjee and fire brigade sources said. An electrical fault is suspected to have caused the fire.
As a thick smoke engulfed the building, firemen put up ladders to rescue the trapped people, who had scrambled out from windows on the ledges of the building. Several people also clung to the ledges of the building before they were rescued. Hydraulic ladders were also pressed into service.
Stephen Court, located in the heart of the city, houses the iconic 100-year-old Flury's confectionery house and a large music store called Music World and several other offices.
At least four persons were injured after they jumped in desperation from the higher floors of the building, sources said.
Senior police and fire brigade officials were monitoring rescue operations at the spot, which has been cordoned off to facilitate smooth fire fighting operations. The entire Park Street area has been closed to traffic.
"We are trying to save the stores and restaurants as the fire is yet to be brought under control on the fifth and sixth floors," Chatterjee said.
The police have arranged ambulances to treat the injured on the spot.
"It is an old building and as such, its fire-resistance capacity is not known. I can't say if the building can be saved, considering the degree of devastation," Chaterjee said.
Chatterjee said that fire-fighters had gone inside the building and were rescuing the trapped persons one by one.
Landing at the site nearly one-and-a-half hours after the fire broke out, Trinamool Congress chief Mamata Banerjee claimed that she had been monitoring the situation from home as "I didn't want them (the Communist Party of India - Marxist-led state government) to say that my presence hampered rescue operations."
She also took the opportunity to slam the state government's disaster management system, saying, "I was waiting for the fire to die down, but the situation seems to be getting worse".