More victims of a child prostitution ring have come forward, which NSW police say may lead to further arrests of male clients.

Police are continuing to investigate the operation allegedly run by two sisters in southwest Sydney.

They are accused of procuring girls as young as 12 to middle-aged men over a three-year period.

One of the alleged customers is accused of raping a girl as she screamed out for help, despite one of the two sisters, aged 22 and 19, being in the next room.

Liverpool crime manager Detective Inspector Danny Doherty said police had identified more alleged victims.

"There's been information received from some other girls who've come forward who are victims," he told AAP on Friday.

"We're still processing that information and trying to determine if there's any evidence that may identify further clients."

For operational reasons, he would say how many more victims had come forward or when additional charges might be laid.

"At some stage it was a desperate need for them (the victims) to be involved in this sort of activity," Det Insp Doherty said.

"Whether it's through coercion or through being immature."

In May, detectives from Strike Force Woodvale laid 70 charges against the two sisters accused of procuring seven vulnerable girls to four men aged in their 50s.

Sex allegedly took place in cars and motel rooms.

A 12-year-old was allegedly sold for sex three times in three days.

Accused ringleaders Adrienne Garner, 22, and Tahlia Garner, 19, from the Liverpool area, and four alleged customers - Elia Toma, Bassam Darwich, Trevor Weger and Rino Mura - are before the courts.

Police say the sisters targeted young girls who were living rough and offered them illicit drugs before prostituting them.

The alleged offences date back to November 2008.

- AAP