Three people have been charged after a 13-year-old girl was forced to work in the sex trade, Toronto police said Friday.

In October, 2015, the victim and a 17-year-old girl allegedly began communicating on Facebook, where they had friends in common.

Toronto Police Sex Crimes Insp. Joanna Beaven-Desjardins told reporters that the victim was told she could make a lot of money working together the female and her boyfriend. During the conversation, the victim told the teen she was only 13, Beaven-Desjardins said.

"The female didn't care," she said.

The pair met in person at a home in Toronto, then the teen introduced the victim to her "supposed boyfriend," and a second man, police said.

The three people then allegedly told the victim she'd be taken to Niagara Falls to provide sexual services to prospective clients, police said.

"The victim told them that she did not want to engage in these acts. However, she was advised it was no longer her choice, and was threatened with physical violence," Beaven-Desjardins said.

Police said photos of the victim were posted in online ads, and she was forced to perform sexual services in Niagara Falls, Brampton and Toronto. She was forced to turn in all money earned through the acts to her captors, police said.

During that time, it is alleged that one of the men sexually assaulted the victim on three separate occasions. She was also beaten by the man, Beaven-Desjardins said.

Fearing for her life, the victim fled the home of her alleged captors on Nov. 9. She flagged down a stranger, who called police.

A search warrant was executed, and three suspects were arrested. Police said they also seized several items during the raid, but did not provide details as to what was obtained.

As a result of the investigation, 22-year-old Kahmal Howard Paris was charged with 12 offences related to human trafficking and sexual assault.

Alico Allen, 19, was charged with human trafficking and procuring and exercising control.

A 17-year-old girl was also charged with 8 trafficking-related charges.

"This is a very disturbing investigation," Beaven-Desjardins said.

"The purchasers of this type of service are as much to blame as the predators."

She asked anyone with more information on the investigation, or on those who solicit sex with minors, to contact the Toronto Police Sex Crimes Unit.

Police believe there may be more victims, who are asked to call investigators at 416-808-7474, or Crime Stoppers anonymously at 416-222-8477 (TIPS).