No casualty has been reported so far, he said.
Thirty fire tenders have been pressed into service to douse the fire.
"As the area is very congested, we are finding it difficult to work. We are using hydraulic ladder and gas cutters to cut through the grills of the gates and small windows to enter the building," the senior official said.
The fire broke out on the ground floor of the building and spread to other floors, he said.
"Even after five hours, we are finding it difficult to contain the fire," he added.
Traffic restrictions have been imposed in the area due to the fire.