Phoenix, Ariz. -- A pair of 16-year-old girls face child prostitution charges for their roles in what police described Monday as a sex operation where the girls recruited and managed other teen girls as young as 14.

Phoenix police vice detectives investigated the girls for nearly five months before making separate arrests earlier this month. The case was investigated separately from the weekend prostitution sweeps led by the FBI, in which Phoenix police made more than 50 arrests.

Police believe Jazmine Finley and Tatiana Tye recruited as many as five other high school-age girls for the sex trade, though no sex crimes occurred on campuses, according to Phoenix Sgt. Andy Hill.

At one point, the girls rented a central Phoenix apartment to host their business - "operating as business owners as part of this criminal enterprise," Hill said.

Finley faces nine counts of child prostitution, among other charges. Tye has one charge of child prostitution and three charges of pandering.

Police say the county attorney plans to prosecute both teens as adults.

Detectives began their investigation into the girls after Phoenix Maryvale Precinct officers, who noted child prostitutes working the neighborhood, called attention to an area near Van Buren Street and 27th Avenue.

Additional arrests could be made in the case, police said.