The blaze erupted on the first floor of the four-storeyed 'Mehta Mansion' in Girgaon at around 8:15 PM, they said.
The fire then spread to the second floor of the complex, the officials said, adding no casualty or injury to anyone has been reported in the incident so far.
According to them, eight fire tenders have been pressed into service.
Earlier in the day, a fire broke out in a residential building on P D'Mello Road.
However, no one was injured in the incident. The blaze had erupted on the first floor of the ground plus three storey building 'Sai Niwas' near Kaisar Hind Hotel at around 3:45 PM, a fire brigade official said.