Authorities say they've uncovered a massive international sex trafficking ring in Southern California. Prosecutors announced the arrest of four people connected to the Orange County-based enterprise that allegedly placed thousands of ads for sexual services in 29 states over the past two years. The ring was based locally in Irvine. Women and girls from China were forced to sell themselves for sex and sometimes forced to work 14 hours a day in homes purchased specifically for the purposes of prostitution. Investigators tracked the ring through thousands of ads selling sex on Backpage.com. There's a townhouse in Cottage Grove [Minnesota], that was bought and paid for with cash. And when police entered, they saw two beds. That's it. But they also saw a line of guys waiting on a couch, waiting for their turn," said Pete Orput, an attorney with Washington County. The actual bust took place in Minneapolis but ... two of the ring leaders live in Irvine. Advocate Jim Carson helps rehabilitate victims of human trafficking in Orange County, and says Irvine might be consistently named as one of the safest cities in the U.S., but not for the young women he helps. "I think the tip of the iceberg, we hear about [trafficking data], we go, 'my God these numbers are so huge', but I honestly think it's much, much bigger than people realize," said ... Carson. He says on just one day recently between 1-9 p.m., he saw 51 ads on Backpage.com for escorts in Irvine. "Every ad on that internet, they're seeing five to twenty dates a night," said Carson.