Transcript for Stunning landscape of tribal nation on US-Mexico border hides dark reality
This is an undercover federal agent disguised as a Mexican drug smuggler. That is 200 pounds of confiscated marijuana, and this is a sting. Today a tracking device is being inserted in one of the bales. Uc is in contact with a tribal concentration cell. They've hired someone to pick up the 200 pounds of weed. So let's move on this. Reporter: In this operation, the undercover agent is using confiscated drug to bait drug dealers. We've told them we have marijuana to be transported. Reporter: Matt hall is the supervisory special agent for an immigrations and customs enforcement task force that operates on a native-american reservation in Arizona that lies along the u.s./mexico border. We're going to be building the wall. Reporter: At a time when border security is dominating our national debate. They're bringing drugs. They're bringing crime. They're rapists. Reporter: This reservation has become a significant, but little known, point of vulnerability. After years of being targeted and kruntsed by perhaps the most notorious criminal organization on Earth, the sinaloa drug cartel. We're in the middle of the sonoran desert on a popular drug trafficking route. In just a few minutes we're expecting a tribe member to pull up in a vehicle and he will load ten bales of marijuana that are here in the desert with an undercover agent. He appears to be flagging him down. Back open. Contraband's being loaded into the sedan. Sid, confirm the tracker's working. Tracker's working. Car is on the move. Car is on the move. I've got eyes on the vehicle. Let's keep a long eye there. Okay, I think I have him in sight. They're about to turn on Valencia. Hey, guys, they're taking bundles out of the car. I'm going in, guys. Reporter: But when the suspects try to move the drugs to another vehicle, the agents move in. They're taking off, southbound, southbound. Southbound. Reporter: Just as the team is arresting several of the suspects. As you can see, they have multiple suspects under -- Get in the car. Reporter: Agent hall receives word that two other suspects are attempting to escape on foot. Got'em, got'em, got'em. Kevin, just keep a distance. Two young girls. Don't move. Keep your hands where I can see them. Put your hands on your head now. Get down on your knees. Keep down on your knees, face away from me. Don't move. Do you understand me? Do not move. Reporter: These suspects are Two in custody, two in custody. Reporter: I can see why this is a good bust for you, but it's also sad. Well, we have to get down to the bottom and see what it is, but, you know, every, as we talked about, they take advantage of every different make, model and age of people. Where do you live? Where's your parents at? I don't have any. Reporter: The adrenaline of the chase now gives way to the kind of depressing reality of the people who've been arrested who do not appear to be drug kingpins, more likely that they're people without a lot of options who've gotten Coe opted by one of the most powerful drug cartels on Earth. Reporter: The nation, the third-largest reservation in the U.S. Is about the size of Connecticut. Its stunning desert landscape takes up more than 60 miles of the border with Mexico. But the tribal elder says the beauty of this land belies a dark reality. Whether it's my house or whichever house, you couldn't go very far without finding another house where someone's either been arrested, is involved or has been involved in that type of activity. With the drug trafficking, human smuggling. It's so normal. And that's not right. Reporter: Juan says the sinaloa cartel has taken advantage of the rampant poverty on the reservation by offering to pay people here to smuggle drugs and migrants. I see more hurt, more struggling, more confusion, if you will. I see the brokenness in the people. Reporter: For Juan, this is personal. He used to run drugs himself. He fears that his children, even his grandchildren, could get pulled into criminal activity. Now he is a pastor, and he spends his days tending to his Thank you for everything you've blessed us with. Amen. Reporter: And trying to keep his children and community on the right track. The people out here, it's hard. It's hard to live. Whether lack of jobs and poverty than other opportunities open up that aren't good for our people. Nothing really to do out here. No economic development, stuff like that. Gives you nothing to do. Except for like trouble. Gangs, drugs. There's some bad things here. Even though there's a lot of good, there's a lot of stuff. It's a small town, but there's a lot of crazy things that happen. We're going out to serve some federal arrest warrants. Police, come to the door! Reporter: As the task force rounds up members of the tribe suspected of working with the cartel, the level of poverty here becomes clear. More than 40% live under the poverty line. And remember, this is America. Is there anything inside the house illegal that we need to know about? Hm-mm. You want to talk to grandma before we leave? Stay right there, grandma, you can come outside if you want. So he has a warrant for his arrest. For what? For conspiracy to smuggle narcotics. I think that there is a very deep-rooted involvement in smuggling. It's gone on for generations. Reporter: In March alone, agent hall's team was responsible for seizing about 30,000 fentanyl pills and other illegal drugs right here on the reservation. It's a wide open area that's not always the most patrolled by law enforcement. Reporter: Agent hall has been working on native-american reservations since he was a 18-year-old rookie, which gives him a nuanced perspective on tribal communities now that he's leading the drug smuggling task force here. We really have to balance the sovereignty, culture and all those things that come with being on a reservation. Reporter: The people were here long before there was an international border. When westerners arrived, their culture was decimated through the introduction of disease and alcohol. By the early 1900s, their vast ancestral homeland had been dramatically reduced in size and carved up between the U.S. And Mexico. We traveled south of the border where there are still about 2,000 of these people living this is where the sinaloa cartel's operation to run drugs up through the reservation begins. Here we meet tribal member matthias. There are a lot of members who are deeply involved with the cartel here in Mexico. Reporter: He says he's been approached by smugglers with lucrative offers. Some one from the group asked me to drive a truck with a hidden compartment onto the reservation and drop it off and they were willing to pay me $10,000 just for a two-hour trip. Reporter: He declined that offer, even though it would take him about a year to make that much money from his regular salary. But not everyone can resist the cartel. Another group they target, migrants who can't afford to pay thousands of dollars to cross the border with one of the cartel's guides known as coyotes. We met 17-year-old Elmer from Guatemala who says he's lost both of his parents. Reporter: In order to pay off his debt, Elmer will become part of the drug pipeline that runs through the reservation. You want to work with the mafia to raise the money? Reporter: Back in the united States, it is this never-ending flow of desperation that agent Matt hall and his team are up against. Tonight they say they're tracking a tribal drug runner picking up a truck filmed with marijuana that's been supplied by an undercover agent. Across the parking lot. There. I'm parked just north of it. In the Walmart parking lot. Reporter: They suspect the tribe member plans to transport the drugs deep into the interior of Arizona, well off the reservation. Break, break, break. The vehicle's getting occupied right now. Go. Reporter: That pickup trick has a kill switch in it, allowing hall's team to turn off the engine remotely. It's making a u-turn. God damn it. Vehicle's traveling at a high rate of speed. Use the kill switch. Get up here and kill it.
This transcript has been automatically generated and may not be 100% accurate.