The two accused have been arrested.
The incident came to light in the wee hours on Friday when the woman, a native of the northern state of Uttar Pradesh, was spotted lying in a duct of the building in the Pydhonie area here.
Acting on a tip-off, the Pydhonie police rushed to the spot and admitted the woman to a state-run hospital.
“The Pydhonie police has registered an offence of gang rape and arrested the two accused. Further investigation is on,” Deputy Commissioner of Police, Zone-II, Dnyaneshwar Chavan said.
The woman was allegedly raped on Thursday night by the two persons in a house on the fifth floor of the building.
She had come there with one of the accused, whom she knew previously, another police official said.
The accused had brought her to Mumbai 10 days back on the pretext of getting her employment, he said.
Both of them stayed in Bhiwandi township of the neighbouring Thane district for eight days where she was also allegedly raped by him, he said.
They came to the building in Pydhonie on Thursday at the godown cum residence of the other accused, he said.
The woman and the two men had dinner together after which they allegedly raped her, the official said.
At around 4am , she was spotted in the duct of the building by some residents.
Police said the woman fell in the duct while trying to run away from the house while the two accused were asleep.
She suffered serious injuries and has been admitted to a hospital, the official said.