SALEM — A man and woman in Beverly have been charged with prostituting young women in a Salem apartment, following an investigation by the attorney general's office.

Woonryong Heo and Hayun Nam, both 29 and living at 480 Rantoul St., Apartment 309, in Beverly, were arrested Wednesday afternoon on Rantoul Street by state police.

Both are charged with human trafficking, deriving support from prostitution and money laundering. Nam is also the subject of a federal immigration civil warrant for being in the country illegally. 

The investigation began when state police investigators found online ads picturing young women in provocative poses and promising "a sensual experience," along with a phone number, according to court papers.

When investigators called, a woman answered and gave them directions to an apartment in Salem. Police began staking out that address, which was not included in any court filings, and confronted several men as they left the apartment.

The men told the troopers they had just paid $140 to $160 for sexual acts with an Asian woman.

The surveillance continued, and investigators saw a man and woman, later identified as Heo and Nam, visit the apartment one to two times a week, sometimes bringing groceries and sometimes taking out trash. 

No one living inside the apartment was ever seen outside alone. Instead, investigators saw young women arriving in Ubers, a woman leaving in an Uber that dropped her off at South Station, and a woman being driven to Flushing — a neighborhood in Queens, New York — in the pair's Honda Odyssey minivan. 

Investigators confirmed the pair's identity when they conducted a traffic stop of the Honda. 

However, the investigation continued. The lease to the apartment was signed by Heo last October, and he used the same email when he rented the Rantoul Street apartment. 

In addition, he used the same phone number when he signed the lease on the Salem apartment as the one in the ad, investigators said. 

Bank records obtained with a search warrant showed that Heo and Nam had as much as $150,000 in a bank account, and that "numerous" cash deposits involving thousands of dollars at a time were being made. 

The amounts of money being banked did not square with the couple's known sources of income: Heo was also occasionally driving for Uber and was seen picking up checks from a nail salon. 

State records show that Heo incorporated a business called "Smile Nail and Spa" last September. 

Both pleaded not guilty to the charges at their arraignments on Thursday, where Judge Emily Karstetter set bail at $50,000 each.

Nam is also the subject of a federal immigration detainer, a type of civil warrant issued by the Department of Homeland Security, which says she "either lacks immigration status" or is someone subject to removal.

Karstetter set conditions of their bail that include house arrest, GPS monitoring bracelets, and surrendering their passports. They were also ordered not to have any contact with the person that prosecutors have identified as the victim, and may not leave the state. 

Court documents do not reveal the location of the so-called brothel in Salem; a document containing details about the victim was ordered sealed by the judge. 

Messages left for attorneys for the pair were not returned Friday afternoon. Court papers indicate the lawyers were appointed to represent the two only for their bail hearings on Thursday and they may no longer be representing them, however. 

A probable cause hearing is scheduled for March 14. 

The attorney general's office has charged more than 40 individuals with human trafficking or related charges since a new statute targeting that crime went into effect, the office said.

Many human trafficking cases involve women who are lured by promises of legitimate employment, only to learn upon arrival that they will be forced to work as prostitutes.

Along with the state police, police from Salem, Beverly, and Lexington were involved in the investigation, as were investigators with the state Department of Correction. 

Courts reporter Julie Manganis can be reached at 978-338-2521, by email at jmanganis@salemnews.com or on Twitter at @SNJulieManganis.