Chicago- from www.suntimes.com – An undercover prostitution sting on the Northwest Side this week led to the discovery of an elaborate video recording system used to videotape transactions and sex acts between the suspect and her clients, according to police.

Guo Yu, 53, was arrested Monday in her apartment in the 5400 block of North East River Road in an unincorporated area near O’Hare Airport after Cook County Sheriff’s police investigated an ad on an Internet site, according to a release from the sheriff’s office.

She was charged with prostitution, according to a sheriff’s office spokesman.

The ad promised a “superb authentic oriental rub” by a 28-year-old “beautiful, highly trained and skilled young lady” who “is there to please.” For $180, customers were promised an “all inclusive” “tissue rub” and “a totally relaxing experience” in a “beautiful home, in a relaxing oriental setting,” the release said.

An undercover sheriff’s officer responded to the ad Monday afternoon and once inside, Yu allegedly offered sex for cash, the release said. She briefly left the bedroom for another room, where she had set up a video monitor connected to a camera hidden in the hallway outside her apartment door.

On the monitor, Yu saw officers outside her door and though she was naked, she nervously returned to the bedroom and tried engaging in conversation with the undercover officer, who placed her under arrest.

Investigation revealed a hidden camera in the public hallway and more cameras in the bedroom, including a pin-sized camera set an Oriental wall fan. Jamming equipment had also been set up to block cell phone or text message transmissions from the apartment, the release said.

All cameras all fed into a kitchen monitor for viewing, and were recording on a system set up in another bedroom. Years’ worth of tapes were found, all showing male customers exchanging cash for sex, the release said. About 30 hours worth of tapes have so far been confiscated, and more tapes had been erased.

Officers are reviewing the tapes for evidence and examining a computer found in Yu’s home. It is illegal in Illinois to videotape a person without their consent or to transmit live video of a person without their consent, the release said.

Police are also trying to determine whether any of the tapes were used to further other criminal activity against the customers.

Yu’s next court date is set for March 25 in Rolling Meadows.