Two women used the online classified site Craigslist to offer sex with girls in exchange for "donations" or "roses" — code words for money, police said.

Tamara Cotton, 25, and Christina Holt, 19, were arrested separately and were not working together, Cook County Sheriff's officials said Thursday.

Cotton was arrested Dec. 31 when an undercover officer arrived at her apartment and a 16-year-old girl offered to perform a sex act for $200, according to the sheriff's department.

While out on bond, Cotton was arrested again on Jan. 5 when she allegedly drove another girl to meet an undercover officer who had arranged a sexual encounter. Cotton was charged with pimping and related offenses.

Police arrested Holt on Monday and charged her with keeping a house of prostitution for allegedly arranging a sexual encounter with a 14-year-old girl.

The three minors arrested were not taken into custody, sheriff's spokeswoman Sally Daly said.

"We've considered them to be more the victims in this case, given the fact that they were being pimped by adults," Daly said.

The Craigslist ads answered by the officers offered sex acts in exchange for "donations" or "roses" — meaning money, according to police. The ads featured photos of unidentified women.

In an e-mail to the Chicago Tribune, Craigslist CEO Jim Buckmaster said the site prohibits illegal activity and intends its erotic services page for "legal escort services and sensual massage providers."