Federal prosecutors indicted six people on sex-trafficking charges last week after an FBI sting identified brothels operating in Beaverton, Tigard and the heart of downtown Portland.

After a yearslong investigation, federal officials built a case against a sex-trafficking ring that allegedly spanned more than four dozen cities and three countries. Prosecutors say the "bosses" who ran the brothels brought young women from China and other countries in Asia who spoke little or no English and forced them to perform sex acts for money.

In June 2016, neighbors started calling the Crime Stoppers tip line.

"International prostitution ring operating in Portland," one tipster said, according to records reviewed by WW. "When will you shut down this operator? They offer unprotected sex acts. [Thousands] of people are at health risk."

At one suspected brothel in Southwest Portland, a property manager received an anonymous letter in May 2018 that was shared with investigators: "Just a heads up, but you have Chinese prostitutes working in your apartment now. I suspect they just took out the lease recently. But you definitely want to get rid of them ASAP…. You will have men coming and going all day, and not good people."

Police searched some of the apartments and found the tenants often had few pieces of furniture other than a bed with a single sheet and a towel laid over them. The closets were empty except for lingerie. The bedside lamps illuminated red light bulbs.

Online ads on sites such as backpage.com and supermatchescort.com, both of which have been seized by the FBI, connected johns to brothels hiding in plain sight. Investigators set up cameras outside suspicious buildings to record customers coming and going.

The operation was run out of hotel rooms, condos and apartment complexes throughout the Portland metro area, according to a federal search warrant authored by an FBI agent. The traffickers even kept a woman in a downtown apartment building on Southwest Jefferson Street across from the Portland Art Museum and just 10 blocks from the federal courthouse.