None of the roughly 40 people who watched the live video reported the attack, according to police, who learned of the attack from the victim's mother.
The video is the second time in recent months that the Chicago Police Department has investigated an apparent attack that was streamed live on Facebook.
In January, four people were arrested after a mobile phone footage showed them allegedly taunting and beating a mentally disabled man.
The girl's mother told police on Monday her daughter had been missing since Sunday and provided screen grab photos of the alleged assault.
Police spokesman Anthony Guglielmi said the department asked Facebook to take down the video, which it did and detectives found the girl and reunited her with her family.
He said the girl told detectives that she knows at least one of her alleged attackers, but no arrests have yet been made.
Guglielmi said it's distressing that there were "40 or so live viewers and no one thought to call authorities".
