this is "nightline." tonight on the front lines. the president promising again to build that wall. >> and we should have close to 400 miles built. >> while our cameras are on the border rolling as a u.s. sting goes down. tracking 200 pounds of weed, suspects caught and cuffed. the sinaloa cartel preying on vulnerable americans to do their smuggling. >> two young girls. don't move, keep your hands where i can see them. >> plus the cartel next door inside the sophisticated techniques to stop and track the drugs coming in over the border. >> here's kill switch. get up here and kill t >> and we're with the sinaloa syndicate inside their drug

labs. so this is a kilo of heroin. >> from production to packaging to smuggling. the escape plan as drug runners move their prized narcotics to the u.s. "nightline" will be right back. (dad) this i(mom)eam cake needs a freezefreezer's full. (vo) only frigidaire's custom flex temp drawer can switch from fridge to freezer. (son) nice save! (vo) that's using your frigidaire.

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vitriolic debate over border security, the president was out touting his wall again today. we have a hidden and horrifying story from the u.s./mexico border. the sinaloa drug cartel, cynically enlisting americans into a relentless campaign to move drugs and migrants into this country. 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 cop s 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, ista younirls 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 really young. >> 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 flock. >> 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.n.n.n. >> 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 >> 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 today. 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 toro 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. [ speaking in foreign language ] >> 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

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vehicle's traveling at a high rate of speed southbound. >> reporter: tonight, superviso supervisory special agent matt hall and team are tracking a drug runner working for the

sinaloa cartel, but their remote device to kill the suspect's engine doesn't work. >> kill it, kill it. >> reporter: moments later, they find the truck crashed in a wooded area. >> do we have the vehicle? we have the target? yeah, we've got the vehicle. it's catching on fire. >> the driver got out and ran, apparently. >> break 179. >> reporter: the agents prepare for a confrontation. >> 10-4. >> reporter: but in the darkness and disorder. >> we don't have the target. >> reporter: the suspected tribal drug runner gets away. yet another member of the nation coe opted by the sinaloa cartel. recently, we took a trip to the cartel's home base in sinaloa, mexico to see first hand in the

inner workings of the criminal organization that has such a stronghold on the reservation and the drug trade in america. the contrast is mind-bogglinwee this place and the amount of devastation this product creates for regular families in ohio and vermont. it's just incredible to watch this process play out. they move around from spot to spot to do their cooking. and evade the authorities. so this is a kilo of heroin. [ speaking in foreign language ] >> reporter: this car will go to the border with this amount of

heroin in your car. >> yeah. >> reporter: our president, donald trump, is talking about building a big wall along the border. would that significantly damage your ability to get drugs up into the united states? [ speaking in foreign language ] >> those outside forces that are creating a bad storm for our people. >> reporter: former drug runner now pastor jay juan says many tribal members feel trapped, threatened by the power and influence of the sinaloa cartel from the south but also angered by the federal government's constant presence on the reservation. >> we're being bombarded on every side. and as all them people, we'll have to sacrifice something. >> reporter: juan says the

border patrol at times acts aggressively toward tribal members, demeaning them on their own land and has even been accused of corruption itself. >> not all of the border patrol are bad, but it only takes a few to create this image or this fear. >> reporter: juan's son jeff says he's been detained multiple times under suspicion of criminal activity. >> they came, tried to tackle me, threw me down on the ground. boots on my back. >> we sat there for a good hour and a half. they're like, all right, you're good to go home. i'm like, what? >> reporter: people here have long been frustrated by border patrol, but now they're also fearful of president trump's proposed border wall, which they say would destroy sacred sites and be utterly impractical on this rugged terrain. >> i invite the president of the united states to come here and walk the 62 miles with me. invite everybody else to come down here to see why a border wall will not work here.

>> reporter: ver lynn jose, second in command of the tribal government says the nation cooperates with federal law enforcement but chafes at any idea that his people are to blame, not when america's appetite for narcotics persists. >> the situations we face are not created by the nation. the drugs coming through this nation are intended for your citizen towns across america. >> reporter: pastor juan says he's less concerned with casting blame and is instead focussed on how to help his family and community, which has endured so much painful history. >> we maintain our uniqueness, whether it's our culture, our language, where we live. and yet move forward. >> reporter: that, he says, is going to take sustained, economic and educational investments in this often-neglected community. but the pastor knows all too well the powerful forces he and his people are up against.

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and finally here tonight we have an update on the tribe. while tribal leadership still opposes president trump's border wall, late last month they did reluctantly agree to a so-called virtual barrier composed of radar and surveillance equipment. their hope is that this will help reduce the law enforcement footprint on their lands. we want to thank you for watching "nightline" tonight, and we wish

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