Updated

Nine Chicago gang members have been arrested for allegedly selling young girls and teens for sex in what authorities have described as a massive human trafficking investigation, MyFoxChicago.com reports.

Cook County State's Attorney Anita Alvarez said the probe was the first in the nation to use state wiretaps to track the alleged offenders running the sex trade, according to the station.

A 35-page police affidavit, called "Little Girl Lost," reportedly states that girls as young as 12 were part of the sex ring.

The girls were allegedly drugged, beaten and threatened by gang members, the station reports. Some endured face slashings and were forced into the trunks of cars for long periods of time as punishment, according to authorities.

"I've worked approximately 23 years in sheriff's department, the last 12 I've done child exploitation crimes and this is the worst with what we've seen, the beatings, the manipulation, the violence involved," Mike Anton of the Cook County Sheriff's Department told the station.

"In one case, we saw where a 13-year-old girl was sold from one pimp to another for $100 and what we've noticed is gang members are loosely connected to each other and sell girls to each other," added Alvarez.

Click for more on the alleged sex ring from MyFoxChicago.com

9 Arrested in Chicago Sex Trafficking Investigation: MyFoxCHICAGO.com