Police announced the arrest of two homeless men late on Wednesday who are suspected of taking part in the assault and robbery of the 51-year-old victim on Tuesday.
The tourist, traveling alone and in Delhi after visiting the Taj Mahal, had lost her way as she returned to her hotel in the main backpacker's area and apparently approached the group for directions.
"We have already arrested two of the eight suspects in the case and are still carrying out raids across different locations to nab others," Additional Commissioner of Delhi Police Alok Kumar told AFP.
The senior police officer said that all the accused were "young men, mostly vagabonds" and that they had assaulted the victim for almost three hours at knife-point.
More than 15 homeless men were rounded up for questioning on Wednesday around the crime scene, a secluded part of gardens near the New Delhi railway station.
"The arrest of two men has revealed identities of the other accomplices and we are looking for them," Kumar told AFP.
Last month, India marked the first anniversary of the death of a student who was gang-raped on a moving bus in the capital, in an attack that sent shockwaves across the nation.
Despite tougher laws and efforts to change attitudes to women in India's deeply patriarchal society, the number of reported sex crimes continues to rise.
Source: APP/AFP