While Naseer Hyder, 23, has been arrested, his four friends who aided him in the crime are on the run.
The victim was sitting with her male friend in a car near her apartment on Thursday midnight when four men alighted from another car, forcibly got into their vehicle and drove them away.
Both were taken to a nearby railway track where three men forced the woman's friend out of the car, while the fourth allegedly raped her in the vehicle, the official involved in the probe said.
He said the gang had also demanded Rs 50,000 from the duo, which they did not have.
The man who allegedly sexually assaulted the girl was arrested and a case booked against him under various sections of IPC, including section 377 (unnatural offences), 354 (assault or criminal force to woman with intent to outrage her modesty), 376 (punishment for rape).
A hunt is on to nab others involved in the incident. The complaint was lodged on Sunday.
