A minor fire broke out at a BSNL exchange in the basement of Air India's eastern zone headquarters in the central part of the city on Friday.

The fire, suspected to have been caused by a short circuit in an air-conditioning machine, was extinguished within 40 minutes by fire tenders, authorities said.

Though the BSNL claimed that no equipment was damaged, around 1,000 landline connections handled by the exchange were affected for the rest of the day as the systems were “deliberately shut down” to avoid any accident.

An Air India spokesperson said the building's fire alarm bell went off around 12.30 p.m. and dense smoke was sighted in the basement.

“Since the basement did not have an effective ventilation system, the smoke could not escape and created panic among the employees.

“A short circuit in an AC machine appears to have started the fire, but it was doused within a short time,” D.P. Biswas, Additional Director-General of Fire Services, said.