TYNGSBORO — A massage parlor operator was arrested after an investigation allegedly revealed sexual acts taking place inside the business, leading to charges including keeping a house of prostitution.

Authorities said the case, which led to the arrest of Chun Xiang Cao, 60, of Lancaster — operator of Healthy Wellness Spa on Middlesex Road — is tied to a Somerset massage parlor raided in July during a sex-trafficking investigation.

A Tyngsboro Police incident report states the investigation into the massage parlor located in Firehouse Plaza at 130 Middlesex Road began in May after a Somerset detective alerted local officers to an ongoing criminal probe into Lotus Flower Wellness Spa in their town.

That investigation, which began in March after concerns about possible human trafficking and complaints of sexual activity at the business, led to the arrest of Yuehong “Yoyo” Wang, 53, on charges including trafficking a person for sexual servitude and deriving support from prostitution.

According to the incident report, while conducting surveillance of Lotus Flower Wellness Spa, police allegedly witnessed a gray 2026 Honda CR-V registered to Cao transporting women to and from the Somerset business on multiple occasions.

Police said the two businesses were also tied together by a check from Lotus Flower Wellness Spa that was deposited into an account for Healthy Wellness LLC and endorsed with Cao’s signature.

The Secretary of State Office’s corporate database identifies Cao as the president, treasurer, secretary, CEO and director of Healthy Wellness Inc.

Police said they further established that Cao and Wang shared a Waltham address and had ties to individuals with a criminal history related to acts of prostitution and unlicensed body massage. The connections, combined with surveillance patterns, suggested the two businesses were operating in tandem, they said.

Healthy Wellness Spa notes on its website that it is open 12 hours a day, seven days a week. The business describes itself as “professional and unique” and offering “professional bodywork experience at affordable prices.”

Police said in the incident report that the massage parlor was also advertising on several online sites, including “Skip the Games” — a platform police described as “a known website for businesses and persons to advertise sex for a fee.”

According to police, the listing featured images of Asian women in revealing clothing and promoted “ULTIMATE BODYWORK” and “COME SEE OUR NEW GIRL!” with prices ranging from $50 to $110. The phone number included on the platform matched the Tyngsboro massage parlor.

Beginning in May, the Tyngsboro Police and the State Police conducted surveillance at Healthy Wellness Spa. Police said that officers reported seeing a steady stream of male customers entering the business, often staying between 20 minutes to an hour.

An officer noted in the report that he observed the business was “being frequented by a high number of male parties,” while he “did not observe any female patrons of the business during this time.”

Police said a sign on the massage parlor’s back door depicted a woman on a stripper pole with the phrase, “work for it,” and “after hours,” and on several occasions the door was open with people coming and going.

Cao’s vehicle was parked in the front parking lot on a regular basis, including being left there overnight.

At one point during surveillance, police said they observed Cao “speaking intensely” with a woman estimated to be in her late 20s or early 30s outside the massage parlor. According to the report, the woman at one point stood with her arms crossed and back turned toward Cao. Cao then followed the woman back into the massage parlor where they remained until the following day.

During the investigation, police also interviewed several men who had visited the massage parlor. Police said some denied any sexual activity, while others admitted receiving sexual acts during massages.

One man said — echoing similar accounts — that “he doesn’t have to ask and they don’t offer, they just do it,” the report states. Another man told police the sexual contact “just happened.”

Their accounts followed a similar pattern, with men paying $50 to $110 for a massage, disrobing in a private room, and receiving sexual contact from a masseuse at the end of the session. Tips ranged from $20 to $80.

One man told investigators he had visited the spa roughly 50 times since 2023.

Each man was told by police to avoid further contact with the business, according to the report.

Police said the pattern of activity, combined with Cao’s movements and associations, suggested she played a controlling role.

In the report, an officer wrote, “I know from my training and experience that individuals who are victimized in human trafficking often have a person overseeing their actions, commonly referred to as a ‘handler.’”

“Observations of Ms. Cao transporting females to and from locations, her association with Yufang ‘Michelle’ Li and Charles Masone — both of whom have prior criminal histories related to prostitution and unlicensed body massage — and her interactions with an Asian female outside (Healthy Wellness Spa) and her coordination of payment inside the business suggest her significant role in these operations,” the officer said.

Police added in the report that Cao also participated in the sexual acts.

When The Sun contacted Healthy Wellness Spa by phone on Friday, a woman who answered said they could not understand a request to speak with Cao and suggested texting due to a language barrier. Text messages sent to the number did not resolve the issue.

On Saturday afternoon, the business was open and operating, with an illuminated “Open” sign in the window and blinds drawn across the front.

A sign on the door instructed visitors to ring a doorbell. A woman who answered allowed The Sun inside but said she did not understand the questions being asked. She indicated that Cao was not present but told The Sun she would let her know that someone was trying to reach her.

The interior of the business contained curtained rooms, and no other individuals were visible.

Despite the woman’s statement that Cao was not there, a gray Honda CR-V registered to her — the same vehicle noted in the police report — was parked in front of the business.

Cao — who required a Mandarin interpreter, according to court documents — was arraigned by Judge William Travaun Bailey on Wednesday in Lowell District Court on charges of keeping a house of prostitution, maintaining a house of prostitution, and sexual conduct for a fee.

She was released on her own recognizance and ordered to surrender her passport within 24 hours, a requirement she met, court documents state.

Cao is scheduled to return to court for a pretrial hearing on March 11.

Her attorney, Joseph Connors Jr., declined to comment about the case.

Follow Aaron Curtis on X @aselahcurtis, or on Bluesky @aaronscurtis.bsky.social.