Reports say the woman, who works as a domestic helper, was offered a lift in a vehicle by the men and then allegedly sedated and raped.
Pedestrians found her semi-naked on a road early on Thursday.
The gang rape and murder of a student on a Delhi bus in December sparked protests across India.
Delhi police spokesman Rajan Bhagat told the BBC that a case of rape had been registered.
However, doctors at the city’s Safdarjung Hospital said she was suffering from trauma, but there were no signs of external injuries.
“We did not find anything visible, external injuries, and we have stated that in our report. It is now for the police to investigate and establish the case,” hospital chief BD Athani told The Indian Express newspaper.
Reports said the woman, who is married and came from Nepal, was on the way to her brother’s house from her employer’s residence in the up-market Defence Colony neighbourhood when a car carrying the men stopped to ask her for directions and offered her to drop her near her home.
The issue of sexual violence against women and girls has been under intense scrutiny in India after the rape and murder of a student on a Delhi bus in December led to widespread protests.
Six people have been charged over the case which shocked the nation.
Five of them are on trial in a specially convened fast-track court and they face the death penalty.
The sixth accused, a minor, is being tried in a juvenile court. He could be sentenced to three years in a reform facility.
All the six accused have pleaded not guilty.
Last month India passed a new bill containing harsher punishments, including the death penalty, for rapists.