Two persons, who were trapped under the debris, have been pulled out and rushed to nearby Seven Hills Hospital, they said.
There were reports that one person died in the incident but no official confirmation was immediately available.
The mishap took place when a 50-metre section of the Metro bridge came crashing down near Hotel Leela.
Two fire engines and an ambulance have been rushed to the spot, sources said, adding cranes and other heavy machinery have been moved in to clear the debris.
The island city and suburbs received heavy downpour yesterday and early this morning.
This part of the overhead Metro bridge is on crowded Andheri-Kurla road that leads to the airport.
The collapsed bridge is part of the much-delayed 12-km Versova-Andheri-Ghatkopar corridor of the Mumbai Metro.
