IRVINE (CBSLA.com) — 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, officials said.

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, according to authorities.

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 officials said two of the ring leaders live in Irvine – which earlier this month was named as one of the top ten “happiest” cities in America.

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, because very rarely will a girl that’s being trafficked even talk about her pimp or her trafficker, let alone turn them in,” said advocate Jim 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.

In Minneapolis, investigators say four pimps held the woman’s passports, keeping them captive. They forced them to make $800 a day to cover food and rent.

On the streets and in Orange County massage parlors, Carson says it’s not much different.

“They’ll take their passport, they’ll tell them, ‘The police are gonna arrest you and do horrible things to you’, and then they’re stuck here,” Carson said.

“It’s happening everyday, it’s gonna happen when the sun goes down tonight. It happens everywhere,” says one survivor of sex trafficking, Oree Freeman.

Freeman hopes the bust sends a clear message to those willing to buy sex.

“What these women have faced, it’s not right. It’s not right for anyone,” Freeman says.

“It can be anyone’s daughter and everyone should be fighting because it’s everybody’s problem,” she adds.

It’s believed a neighbor of one of the homes in Minneapolis touched off the investigation by calling police.