This article is part five of a five-part series titled "The Business of Illicit Massage." Parts one, two, three and four are also available online.

In early April, Liu Yang of Springfield and Stephen Forsley of Bernardston were indicted on sex-trafficking and money-laundering charges for their alleged role in running fake massage parlors in Springfield. The two, according to Massachusetts Attorney General Maura Healey, ran prostitution-related businesses — the Day Spa and the Health and Relaxation Spa — that were allegedly fronts for human trafficking.

The defendants pleaded not guilty and the case is pending. But the legal takedown is another effort by state officials to dismantle the prolific illicit massage industry in Massachusetts. As WGBH and the New England Center for Investigative Reporting have pointed out over several weeks now, the legal assaults on this illicit industry are more happenstance than strategic.

Lt. Donna Gavin, the head of the Boston Police Human Trafficking unit, would be the first to admit that law enforcement needs to be more aggressive in arresting sex buyers who frequent illicit parlors. But, she said, “You can’t arrest yourself out of this.”

Gavin said shutting down the estimated 200 erotic spas in the state posing as massage or bodyworks parlors requires a combination of legislative actions, law enforcement initiatives and creativity. Gavin said she’s even reached out to Boston area priests, rabbis and ministers for help.

“We're trying to have them get on board, because quite frankly some of the sex buyers are probably sitting in their pews,” she said.

Beyond Massachusetts

There are an estimated 9,000 illicit massage businesses in the United States, as part of a lucrative industry that garners some $2.5 billion a year, according to a recent report by the nonprofit anti-trafficking group, Polaris. From California to Cape Cod, law enforcement and advocates struggle to deter the businesses that profit on exploited women, mostly from Asian countries.

Houston is seen as at the forefront of efforts to fight trafficking in a city where hundreds of parlors are located near restaurants and stores. The nonprofit group, Children at Risk, uses one of the sex buyers’ own tools, a Yelp-like review site called Rubmaps, to track down alleged criminal enterprises.

James Caruthers, a senior staff attorney there, said advocates work with pro-bono attorneys and county officials to shut down businesses that don’t have proper licensing. “We’re looking for places that have a lot of reviews, and that way we know the site we’re selecting is a front for human trafficking or prostitution,” he said.

Seattle has also gotten creative to take these places down. Two years ago, an undercover Seattle cop joined a members-only website called The Review Board. King County prosecutor, Val Richey, explains what happened next.

“As part of that invitation, he started going to in-person meetings of men who were posting information on the board. And [they] had also created a subgroup called the League, after the League of Extraordinary Gentlemen.”

Using a statute that makes it illegal to promote prostitution, Richey was able to charge those “gentlemen” in 2016, making King County one of the first to prosecute users of erotic massage review sites. Holding websites accountable for their role in sex trafficking is also the goal — on a national level — of the recently passed Fight Online Sex Trafficking Act.

The law has created disruption in the sex trafficking industry and an array of sites focusing on commercial sex ads and buyer reviews have been dismantled. Among them, Craigslist shut down its personals section, saying: “We can’t take such risk without jeopardizing all our other services, so we are regretfully taking Craigslist personals offline.”

But it appears Rubmaps has not been deterred. The site has a message to buyers online saying it is suspending billing for U.S. subscribers, but it appears the services remain unchanged.

The Bodyworks Loophole

Anti-trafficking advocates here in Massachusetts say the federal law is a great first step. But Senator Mark Montigny, a New Bedford Democrat, said the state also needs to close what is called the “bodyworks loophole.”

The state law regulating massage therapists does not include what is called bodywork, which remains unlicensed. So, over the years, this legal caveat allowed dozens of storefront shops filled with prostituted women to open under the guise of bodyworks.

Montigny said that may be changing under a bill he has sponsored that has languished in the House. “We're working with the governor and the attorney general and others now, which gives me some hope that we're building that critical mass,” he said.

Jo K. Gray, a legitimate massage therapist who co-founded Inman Oasis spa in Cambridge, laments that those lobbying against closing the loophole include some of her colleagues.

“Unfortunately, there are legitimate bodywork practitioners, like people who study Feldenkrais and people who study shiatsu that may not be able to pass a strict massage therapy licensing requirements,’’ she said. “It's complicated.”

The sheer complexity of the problem has prompted some Massachusetts cities and towns to act on their own. Framingham introduced by-laws in 2015 that forced bodyworks spas to abide by a strict health code, which worked for a while to squeeze out the phonies. Then spa owners got wise, said Framingham Police Sgt. Detective Timothy O’Toole.

They're starting to move back to being massage parlors, where they fall under the state licensing as opposed to the towns or cities,” he said.

By finding a front person — a real massage therapist — and getting licensed as a legitimate spa, these places were able to skirt local regulations. Only the state has the power to regulate licensed facilities — and there are only three state inspectors from Provincetown to Pittsfield.

Citizen Action

Because they feel like regulations don’t work and law enforcement’s hands are often tied, some citizens groups are gathering evidence on their own. In Orlando, Florida, private detective James Barnes started a nonprofit called Breaking Out to do just that.

Sitting in a darkened parking lot one recent night, Barnes took notes that he later shared with Orlando police.

“There's one vehicle in the parking lot, a truck parked in front of the door. I have a tag that I will be running on it. So, we're going to see if the girls inside actually go home or go to another location and get picked up or if they are staying on the premises tonight,” Barnes said.

But law enforcement officials do not recommend this kind of citizen action. Illicit massage parlor operators can be dangerous, and many venues are linked to organized crime.

Other voices call for legalizing illicit massage and other forms of prostitution. But a key study warns that where prostitution has been made legal, human trafficking has proliferated.

Rochelle Keyhan, director of Disruption Strategies at Polaris, would like to see a more holistic “death by a thousand cuts” approach to shutting down illicit massage. She recommends getting law enforcement, lawmakers and local officials to hit businesses where it hurts — their wallets.

“Instead of approaching them as one-off potential prostitution venues, they should be looking at this from an organized crime perspective — looking at the money laundering, the wage and hour potential violations, tax evasion,’’ she said. “At that point they'll be finding the exploiters and traffickers and not emphasizing the potential victims.”

But that’s easier said than done. And in Massachusetts and elsewhere, it is unclear whether there’s the political will to tackle the complicated business of illicit massage.

Phillip Martin is a senior reporter with WGBH News. Jenifer McKim is a reporter for the New England Center for Investigative Reporting, a nonprofit news partner of WGBH News.