Fire Brigade officials said altogether 17 fire tenders rushed to the spot after the blaze was reported from the power sub-station of the private power utility in the morning.
Efforts were made to control the spread of the blaze to nearby areas.
The fire was brought under control in about four hours and there was no report of any casualty or injury, the fire brigade and police officials said.
"The spot of the incident near St Stephens' School is so congested that the fire personnel had to struggle hard to reach there," Fire Brigade officials said.
A foam-laden AAI fire tender from the NSCBI Airport also joined the fire-fighting operation, an airport official said.
According to a CESC spokesperson, at around 11.30 AM today there was a fire at one of the CESC 33 KV Transformers inside the Distribution Station near Dum Dum Central Jail.
CESC personnel on duty immediately alerted the Fire Brigade and other authorities. The affected transformer was quickly de-energised and supply to the area restored from alternative sources.
