The blast, which occurred in front of the Hindustan Unilever building at 10 a.m., also shattered the glass panes of nearby buildings, a senior police officer said.
Though the explosion apparently occurred in the underground power cable of a transformer of the private power utility CESC, the officer said, adding that 'investigations into the incident are on'.
Police Commissioner Gautam Mohan Chakraborty, other top-ranking officers and personnel from the bomb squad have rushed to the spot, besides fire brigade officials.
The place where the explosion took place was near Nagaland House, the liaison office and the guest house of the North-Eastern state.