The fire is suspected to have been caused by an electric short circuit, they said, adding none was injured since the bank was functioning only for half a day today.
The fire, which burnt almost all the files stored in the second floor of the building on Rajaji Road, has been brought under control, they said.
"The fire was reported at 3.45 pm and we initially sent seven fire tenders to the spot. Later, more fire tenders and water tankers were sent to the spot. Though a part of the structure has come down, none is injured," S Vijayasekar, Joint Director, Tamil Nadu Fire and Rescue Services, told reporters near the spot.
The fire is completely under control, he said.