Four Boston area massage parlors have been busted for serving as a secret human trafficking ring.

Dan T. Zheng, 47, of Boston, was arrested today and is facing charges of trafficking of persons for sexual servitude, deriving support from prostitution and procuring support for prostitution. These charges are in connection with allegedly offering sexual services for a fee at massage parlors located in Stoneham, Arlington, Dracut and Boston.

FBI Boston Division Special Agent Harold H. Shaw says human trafficking's prevalence is all too common.

“Human trafficking is a crime that happens all around us, often in plain sight, impacting the safety of our neighborhoods and our quality of life," he said. "When human beings are treated as commodities, they are not only being abused physically, but emotionally and financially."

The investigation began in June with members of the FBI Boston Human Trafficking and Child Exploitation Task Force and Malden Police Detectives taking surveillance of the four massage parlors. Investigators say this operation would not have been possible without the help of the multiple departments.

“This case represents the result of a well-coordinated and collaborative investigation,” said Middlesex District Attorney Marian Ryan. “The defendant in this case was allegedly using businesses in four communities as a front to provide illegal sexual services for a fee while exploiting the women who were employed by her in the process."

Their investigation has led them to believe that male clients were allegedly being offered and accepting, additional services of "a sexual nature" following their massages for an additional fee.

Search warrants were sent out to Lisa Massage Therapy in Arlington, Sunflowers Spa in Dracut, Sunshine Spa & Massage in Stoneham and Rose Health Spa in Boston. There they uncovered that Zheng's employees were allegedly being transported from Boston to the various massage parlors for work.

Zheng has been taken in custody and is expected to be arraigned in the Cambridge District Court.

Special Agent Shaw plans to work with other communities to dismantle similar rings in the future.

"The FBI Boston Human Trafficking & Child Exploitation Task Force will continue to collaborate with our law enforcement partners at every level—in an effort to disrupt and dismantle organizations responsible for this illegal activity," Shaw said.