The crime came to light after a 38-second video was posted to Twitter by one of the alleged rapists and shared on WhatsApp.
The footage showed the teen naked and unconscious while male voices bragged about "at least 30" people having sex with her. The rape allegedly occurred in a favela in Rio on May 21.
The case has shocked Brazil, a country used to high levels of violence, sparking mass protests in several cities. In Rio de Janeiro, which is set to host the Olympics in August, protesters hung red-stained clothes along the iconic Copacabana Beach. They have also marched on the Legislative Assembly.
In Brasilia, police used pepper spray on protesters who descended on the Supreme Court carrying bouquets of flowers and signs denouncing the nation's "culture of rape".
Authorities and politicians have been openly accused of failing to take the girl's allegations seriously and not doing enough to find the perpetrators.
Unfortunately, that sentiment appeared to be an accurate representation of the girl's experience.
She told TV Record that public reaction to the images posted online had left her feeling robbed of her dignity and pessimistic about justice being served.
"I knew there would be no justice, that I would be ashamed," she told TV Record. "In the first moment, I didn't even want to tell my mum.
"It not only hurt me, it hurt my soul, because people judged me, tried to blame me for something which was not my fault. They robbed me, not just in material goods, but in a physical way.
"If I have to wait for the justice system, they've already shown that nothing is going to happen. I am waiting for the justice of God. That might be late but it never fails."
Authorities have tried to mollify the public by transferring the case to a special police unit for crimes against minors and replacing the male lead investigator with a female detective who will work in consultation with the state's social services department.
"I am convinced there was a rape, it's right there in the video, when the guy touched the girl," the newly appointed Detective Cristiana Bento told a press conference on Monday.
"The rape is proven. What I want to do now is verify the extent of this rape and how many people took part."
Ms Bento's comments represented the first time police have definitively acknowledged that a rape took place. Previously, they have stated there were "all indications that a rape had occurred but that they needed more proof".
Authorities said a medical exam of the victim was only performed five days after the incident, hindering their ability to gather physical evidence that would lead to additional suspects and arrests.
So far, police have arrested two men and issued arrest warrants for four others following raids on several favelas (slums) in Rio de Janeiro. Authorities have declined to say how many people they are looking for but local reports claim at least 33 men have been connected to the horror attack.