Four people are facing human trafficking-related charges after police say a teenage girl was picked up by two men downtown, sexually assaulted, and forced to work in the sex trade.

In a news release issued Tuesday, Toronto police said a 17-year-old girl met two men in the area of Yonge and Dundas streets on Dec. 30, 2018.

The men, police said, befriended the girl and gave her drugs and alcohol.

Investigators allege that the men took the girl to an address in Hamilton and they, along with a third man, sexually assaulted the teen.

The girl was then introduced to a woman, police say, and was forced into the sex trade.

Police said photos of the girl were taken in various stages of undress and were posted on leolist.com to advertise sexual services.

The girl was told to provide sexual services to “numerous clients,” police say, and was forced to turn over all money she received.

Over the course of four days, police said, the girl was forced to do drugs, deprived of food and sleep, and physically assaulted.

Investigators said the girl was able to escape and contact police on Jan. 3.

Three of the suspects, identified by police as 35-year-old Charlton Sealy, 36-year-old Shabaka Reid, and 27-year-old Deanna Passera, were arrested early this year.

They face numerous charges, including sexual assault, trafficking in persons under 18, and making child pornography.

The final suspect, who investigators identified as 37-year-old Toronto resident Troy Thornhill, was arrested earlier this month.

He is facing nine charges, including sexual assault, trafficking in persons under 18 years by recruiting, assault, and procuring a person under 18 years.

Investigators say they are concerned there may be additional victims who have not yet come forward and are asking anyone with information about the case or suspects to contact police.