HOUSTON -- A mother has been accused of selling her two teenage daughters to men looking for sex with underage girls, officials told KPRC Local 2 Tuesday.

Houston police said the mother distributed business cards advertising sex with children and negotiated the arrangements.

Investigators said the woman's 16-year-old daughter called them when she got tired of being forced to have sex with men.

The girl told police she was recently forced to have sex with a customer at an apartment complex in the 5500 block of Antoine Drive and another customer in the 6200 block of West Tidwell Road.

The woman's other daughter is not cooperating with the investigation, police said.

The teens are currently staying with their aunt.

The mother and boyfriend have been charged with compelling prostitution of a minor.

Detectives declined to comment specifically on this case, but when talking about prostitution in general, an officer said men seek out underage girls.

"They do go after the younger girls," Capt. Steve Jett said. "They make more money. They are worth more, so to speak."

Houston police and the Harris County District Attorney's Office are working to put a stop to prostitution rings, big or small.

"If it starts getting hot here, the owners move them to another location or trade them or sell them," Jett said.