A one-and-half-year-old infant girl on Monday died of suffocation after a fire broke out at an unauthorised structure built on top of the water pump room of a building at Perry Cross Road in suburban Bandra.Fire brigade officials said the fire started in a structure that was added to the pump room of Shoeb Manzil building and was being used as the residence of the buildings watchman.Electrical wires and household articles in the makeshift structure fuelled the fire, officials said, resulting in choking fumes."A girl, about one-and-half-year-old, was rushed to the Holy Family hospital due to suffocation caused by the fumes but was declared dead on arrival. Another child is currently in the hospitals Intensive Care Unit," a fire brigade official said.The personnel reached the spot and doused the fire within an hour of getting the call.Investigations into the cause of the fire are currently underway, an wholesale ceramic alkali pump official said, adding that using the pump room for residential purposes was illegal and fire officials have been told to file a police complaint.