A major fire broke out today in a five-storeyed building at Colaba in South Mumbai, officials said. The blaze erupted on one of the top floors in the commercial-cum residential building situated near Regal Cinema around 4 PM, said officials of Disaster Control Department of the BMC.However, no casualties have been reported as occupants were quickly evacuated, they said.Ten fire tenders have been pressed into service and fire-fighting operations are underway. Personnel from nearby police stations have also been rushed to the spot.The cause of the fire is not yet known and further details are awaited.