A fire broke out at West Bengal state secretariat, Writers' Buildings, on Thursday causing damage to the departments of Refugee Rehabilitation, Fire and Municipal Affairs.
Fire brigade officials said the blaze broke out at block E on the third floor of the century-old heritage building at around 6.45 am.
Twelve fire engines extinguished the fire in two hours.
Nobody was injured and the extent of damage was likely be limited to burnt heaps of paper, documents and furniture of the three departments, police said.
The cause of the fire has not been ascertained yet and the affected block has been cordoned off, police said.
Forensic experts have arrived the spot to investigate the cause of fire and the extent of damage will be known after the offices open.
Writers' Buildings, built by the British, houses Chief Minister Buddhadeb Bhattacharjee's office and other key departments.
Surrounding roads including Brabourne Road which brings traffic from Howrah station to the building in BBD Bag, Esplanade and other office areas were closed when the fire broke out.
The barricades, which were put up earlier, have now been removed and the road has opened to traffic again, police said.
Security in and around the Writers' Buildings has been tightened, police said.