investigation reveals the scale of prostitution on American streets with shocking results. Just in the last 72 hours, a major FBI sting prerescued 168 children from sex trafficking. Now our sister... See More
investigation reveals the scale of prostitution on American streets with shocking results. Just in the last 72 hours, a major FBI sting prerescued 168 children from sex trafficking. Now our sister network fusion brings us a rare inside look at a working brothel, a world where young girls are bought and sold in broad daylight. ? ? Reporter: We're on the trail of an international trafficking ring. Reporter: My colleague is wearing a hidden camera to try to get a look at their product -- sex slaves. She was just walking down the alley with that guy. I'm not sure how safe this is. Reporter: The sex slaves are height here in your backyard. Girls as young as 12, from south America, and trafficked to cities all over the U.S. Are the girls here pretty? Yes. This is nothing more than modern day slavery. Wars have been fought to end that in this country. This is not something we can tolerate in America. Reporter: On this night, we're in Houston, Texas, filming as a multiagency operation targets a sophisticated network of traffickers and pimps, doing business here in the suburbs. We got a firsthand look inside a brothel, just minutes after it was shut down. As you can see, you've got beds that are here. This is just a makeshift type bed with a drape for a little privacy, but not much. This was a room, so a little bit more privacy. Reporter: So just basically a mattress, a small bed. What we have is places like this, we have a ledger of girls that work here. The Xs are the amounts of tricks they've done tonight, and they will pay him a fee, and grab a napkin, condom, this gel and go to the room. And dozens of men coming in and out of maces like this? Uh-huh. And women having sex, 15 minutes and then just go on to the next guy. Reporter: Authorities believe many of these women could be sex slaves. Brought to the U.S. Against their will. They are the merchandise bought, sold, and traded by a vast international network of human traffickers and pimps. Is this a profitable business this It's the fastest growing criminal enterprise in the world. Think about it, drugs, you sell once. Women and children, you sell time and time again. Reporter: During this raid, many of the women and their clients are arrested. But the pimps who traffic them remain free. The sex slave trade is a global business, and the American market is dominated by pimps and traffickers from one Mexican state. No mace in the world sends more sex slaves to the U.S. At the center is one small city. It disturbing on many levels. They're family led organizations that specialize in trafficking young girls, prostituting them in Mexico, bringing them to the U.S. Reporter: The ring has spread throughout the U.S. From the border towns up Thu Texas and California and up the east coast, all the way to new York. The trafficking ring's hub is in carona peach. This is the end of the road for a lot of girls. Sex trafficking is happening right here? Yes. Reporter: El vin Hernandez is an investigator for the department of homeland security, which coordinates international anti-sex operations. He's helped rescue dozens of women from neighborhoods just like this one. This is a house? Yes, this is a house right here. It's right across the street from a public school. They can house themselves anywhere. If you're not aware of how traffickers operate, you're not going to think anything is wrong. It's just the Normal course of the day. Reporter: What do you see on a regular day here? On a regular day, these streets would be full. Guys would be hanging out on corners, handing out cards to find clients to bring to the brothel houses. This is basically the length of walking I'm going to be doing. Reporter: We want to see inside the U.S. Operation. So we send our colleague out into the busiest part of queens, New York, with a hidden camera, to see if we can get an extremely rare look into a working brothel. I'll try to have a long conversation, all right? Yeah. Do you see him? Okay, so they went around the corner. They're going down this street. Are the girls here pretty? Yes. Yes? She's one of them? Hello, how are you? Good, thank you. Okay. I think maybe it's time for him to come out. Reporter: We're all feeling nervous about his safety, so I call him and pretend to be his wife to try and get him out of the brothel. Hi, honey, how are you? I'm okay. I'm okay. I should probably head back. We're going to be on 37th and 81st, okay? See you there. Coming in. So I'm still rolling. All right. It was like, the basement of a house. You could -- the walls were very bare, and you could hear clearly people having sex. There was a steady stream of men coming in and out of there. Reporter: We can tell you that this brothel is right in the heart of an area on an international law enforcement watch list, an area where pimps from Mexico bring their girls. And this woman was one of them. She's agreed to talk to us as long as we disguise her face. Even on a day like today where you're with us, and you're disguised, you wouldn't feel comfortable walking down the streets of queens? By now, I'm a little bit squared. Reporter: For years, she was held captive by a single pimp and forced to work these streets as a sex slave before she managed to escape. He made me to work almost 24 hours. I saw around 60 -- Reporter: Men a week? No, per day. Reporter: 60 men per day? Yes. So by the end of the day I was meeting. Reporter: Do you think more should be done around the united States to combat sex slavery? I79's going to take a lot of efforts. It's a problem that calls for many, many types of solutions. I think awareness has to be raised, that this can be going on underneath your very nose and people don't know about it. For more on this powerful fusion investigation, check out fusion.net. Up next, getting started
This transcript has been automatically generated and may not be 100% accurate.