Four people were arrested at four separate spas in Watertown, Massachusetts, on charges of sexual conduct for a fee.
Watertown Police said the arrests were made at Season Therapy, Sukhothai, Orange Tree and Nuu Spa.
All four suspects were taken in on charges related to sexual conduct for a fee.
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"I'm not surprised," said Watertown resident Al Carbone. "It became obvious to me a year or two ago that there is something going on here. That certainly wasn't massage therapy."
Carbone says he's had issues with his back for years and walked into Sukhothai when his therapist moved away.
"It was obvious it was just something not legitimate," he said.
Police say they went undercover at the massage parlors on Friday. The women involved range in ages from 30 to 51.
Of the four spas, three are still open.
At Orange Tree, NBC10 Boston rang the doorbell asking for a comment. A woman came to the door and said she didn't speak English well and didn't understand the questions.
At Nuu Spa, it was a similar story, with the woman working inside not speaking English.
At Season Therapy, NBC10 Boston spoke with the owner. She says they don't offer sex and that she's not sure why her worker was arrested.
Police say one of the goals of their sting operation was to identify potential human trafficking, but there was no sign of that.
It's not clear when the women will be in court.