OKLAHOMA CITY - An undercover Oklahoma Bureau of Narcotics agent rescued two women who claim they were forced into prostitution by an Oklahoma City man.

The man was charged with human trafficking, and investigators say they're on the hunt for another suspect.

Investigators took the two women into protective custody after the undercover operation.

An advertisement on the website backpage.com triggered the investigation into Milton Shelton, a career criminal now charged with human trafficking. An OBN agent responded to that ad and quickly discovered the two women were not in that the line of work by choice.

“Two of the prostitutes did say that their pimp had threatened to do bodily harm to them if they did not continue to make money for him,” said Mark Woodward, OBN spokesman.

But that's not how the arrangement between the woman and Shelton began, according to court documents. The woman told the investigator in the beginning, she was promised "she could make a bunch of money" if she went to work for Shelton in Oklahoma City.

That woman told the investigator two days before being moved here to the Biltmore Hotel to work in room 418 she was forced to work across Interstate 40 at a different hotel.

Though, according to court records, the victim said Shelton kept all the money she earned from clients. But she told the state investigator she felt forced to continue to be a prostitute since "Shelton threatened to beat her up if she stopped making money for him."

“It was not just their statements alone that made us feel like they were telling the truth, but also witness statements,” said Woodward.

Oklahoma City police arrested Shelton last month.

Court records show his prostitution-related convictions date back to 1996.

Investigators say they're also looking for another man who goes by the name "VP" who was at the hotel. He's wanted on multiple human trafficking charges.