A portion of a five-storey building collapsed in suburban Khar on Tuesday afternoon, but no casualty was reported, a fire brigade official said.
The incident took place around 2.20 pm when part of a staircase of the residential building, located near Khar Gymkhana, came crashing down, he said.
"No casualty has been reported so far and efforts are underway to clear the debris," he said.
A rescue team was trying to ascertain if anyone was trapped under the rubble, he said.
Four fire engines along with rescue vans, an ambulance, local civic officials, National Disaster Response Force (NDRF) and police personnel rushed to the spot, he added.