San Jose police shut down more than 100 illegal massage parlors in a nine-month citywide crackdown on prostitution, officials said Wednesday, but it’s not clear how effective the stings were in combatting human trafficking.

The businesses either lacked permits to operate or violated city code by being public nuisances and offering prostitution services, according to a San Jose Police Department report.

“We know that these types of illicit activities create serious neighborhood impacts, and facilitate human trafficking and exploitation, so we’ll forge ahead with these efforts to crack down on dozens more in the months to come,” San Jose Mayor Sam Liccardo said in a statement.

Police compiled a list of 191 illicit massage businesses in the city from resident complaints, online sex-for-cash listings and by identifying unusually high concentrations of massage parlors in certain areas. A total of 107 illicit massage parlors were identified by police.

In 2016, the city created an ordinance with stricter regulations for massage businesses. That year, police identified 300 known massage businesses and issued 100 warning letters for noncompliance with the ordinance.

The crackdown came after a January 2018 report from the Polaris Project, an antihuman-trafficking nonprofit, said that Santa Clara County has the third-highest number of illegal massage businesses in the country.

The effectiveness of the police crackdown, however, remains unclear.

Police said it’s “difficult” to quantify how widespread human trafficking is in the city, because victims may be afraid to come forward and traffickers can operate remotely. The department also could not provide the number of arrests made or people rescued from human trafficking.

Landlords notified of new codes regulating massage parlor permits and “erotic online reviews by sex buyers” from police shuttered 81 of the businesses, said Lt. Paul Messier, a member of the San Jose Police Department’s Special Investigations unit.

Undercover officers additionally found 54 massage parlors, including some closed by landlords, that were actively offering prostitution services, authorities said. Many of the owners have moved their businesses out of San Jose and relocated in neighboring cities.

“I think what we’ve done is we have pushed this problem into the adjoining jurisdictions around the city,” Messier said. “We have strong codes we enforce, we do undercover operations, and smaller agencies may not have the capabilities to do what we do in San Jose.”

As a result, he added, other law enforcement agencies have asked San Jose police for help in curbing a growth in illicit massage businesses.

Messier said the department is increasing staffing to track dozens of suspicious massage parlors still doing business in San Jose.

San Jose has seen a spike in requests for massage business permits in 2018, officials said. Just this year the city received 67 requests compared to four in 2016 and seven in 2017.

The city now has fewer than 20 fully permitted massage businesses.

Gwendolyn Wu is a San Francisco Chronicle staff writer. Email: gwendolyn.wu@sfchronicle.com Twitter: @gwendolynawu