The three accused have been identified as Vijay S Kharat (23), Datta Badya Dondiram Kamble (20) and Sunil Bhimrao Pradhan (25), they said.
According to police, the trio allegedly took the girl to an isolated place behind the Mamata Hospital near Camp No. 1 area in Ulhasnagar last night, when she had stepped out of her home to go to a nearby market and then took turns to rape her.
The victim lived in a chawl in Ulhasnagar and worked as a domestic help in the township.
Efforts are on to nab the accused, who are still at large, police said.