Four fire tenders have already rushed to the spot along with two hydraulic ladders to rescue any trapped person, fire brigade said.
Since the fire broke out before the office hours, the police said the possibility of any person being trapped in the building, which houses many private and government offices, is less.
The area has been cordoned off to conduct the firefighting operations in the busy area.
There is no news of any injury or casualty. The cause of fire or extent of damage was yet to be ascertained, the police said.