Transcript for Mother's search for missing son has led to a movement in Mexico: Part 1
There's something about being a mother. Why is it so hard to defeat a mother, to make her surrender? I wrote a promise to my son, I will never surrender. I will never give up. Reporter: Lucy Diaz is searching for her son, Luiz, who disappeared 6 years ago. We search for the possibility of a grave. You know, because once we hit on the ground like usually a meter and a half, two meters deep, we smell this bar, and if it comes out with, smells like, well, like a dead body. This is a skill you've developed now to be able to smell for a dead body. Yeah, yeah. And sometimes not only the smell. Once I was hammering this, and I started to hear like a rattle underneath, because it was like not exactly breaking the bone, but it was making a noise, because it was rubbing against the bone. And there was a body. Reporter: Do you think it's possible that right here, underneath our feet, this -- there's a mass grave? It's very likely, yeah. Here in veracruz, it's extremely likely. Reporter: The state of veracruz is known as "Mexico's graveyard," with over two hundred mass graves uncovered here. Reporter: I'm sitting here, watching you guys, mothers do this work, and you have a bunch of cops over here standing here watching you do this, why aren't they doing it? Isn't it the work of the police to fight crimes and find bodies? Keep in mind, this is Mexico. Reporter: Mexico is a country at war with itself. Violence has reached record levels this year. This has been the deadliest year in Mexico in more than two drug cartels waging open gun battles in the streets. Authorities say heavily-armed drug cartel ambushed the military. At least three women and six children were killed in an ambush. Reporter: Tourist destinations degenerating into chaos. Inside that cooler we're told there is a human head. As a result of this carnage, there are by at least conservative estimates 40,000 missing. Riddled with corruption, the task of searching often falls to the most committed, thousands of mothers all over this country. Lucy Diaz was leading a comfortable life as a college professor, mother of three and married to a successful businessman. Everything changed one night in June of 2013. I don't even know what happened to him. At this point, five and half years, and I have no idea. Of his whereabouts or what happened. I know he was kidnapped, but so far, that's all I know. Reporter: At the time, her 29 year-old son, Luis was working as a popular dj in the city of veracruz. He was a staple at weddings and local parties. He was so passionate about his music, and then something like this happened and I just -- I could give him my life. Reporter: One night Lucy got a nervous call from her son's girlfriend saying she hadn't heard from him in a couple days. Lucy called one of her son's employees who promised her that Luis was simply busy at a gig. Then on Monday I said there's something wrong. Because he knows I get crazy whenever I don't -- I cannot get in touch with him. The next day I waited all day. But then, like, around 8:00 I knew. I knew for a fact that it was terribly wrong. Something was terribly wrong. And that's the beginning of the -- of this trip to hell that doesn't have an end. Reporter: The police did talk to that employee who assured Lucy her son was ok. It turned out he was lying. He broke down and said, "No, somebody kidnapped him. I was in the --in the -- in the office. I was in the office, and he was in his bedroom and I saw them come in." Reporter: Lucy also says the employee sold Luis's phone after he was kidnapped. Is he in jail? No, as free as a bird. Reporter: He's just walking around? Yeah. Who's in jail? Me. I'm in the worst jail there is Reporter: And last year, a potentially big break in the case. The police found Luis's motorcycle and the individual who was riding the stolen bike. Hopefully this could lead to answers, Lucy followed up with veracruz authorities. "Did you bring him in, at least, to interrogate him?" And they said, "Not yet." They still haven't interrogated him. Reporter: And do you think it's laziness? No, I think it's corruption. Reporter: Corruption. Yes. They don't really wanna solve the problem. They don't want to find the person. Reporter: But just to be clear, was your son in any way connected to the drug trade, or to the criminal underground? No. And I can say that because, I mean, in six -- almost six years of investigations, the only thing -- the only one that has been investigated in and out and all over is him. They don't leave any privacy to the victim. Reporter: Unwilling to accept investigative inaction, Lucy became a very public critic of the local authorities, a risky move in this deeply corrupt country. Lucy has undergone, she says, an inner transformation from depression to anger so something much larger. She's organized hundreds of other mothers who are desperately searching for their children here in veracruz. We find them raising money by selling tamales at a local carnival, a sorority of anguish. Mothers around a wrenching mission. Reporter: The money that mothers, like rosalia Castro, have raised is used to chase down leads they gather from anonymous tipsters and then launch their search missions. Ms. Castro is one of Lucy's staunchest allies. Reporter: It wouldn't be the first time these mothers have found remains. Just 10 miles from this dump, over 300 bodies were exhumed at a mass grave in las colinas de Santa fe. All the moms say, "Till my dying day." It's like, we're going to fight for our children. There's nothing gonna stop us. Reporter: This struggle has taken over Lucy's life. She quit her job as a professor and now balances her time between working on behalf of all of the mothers and doggedly pursuing her son's case. We take Lucy's case to Karla quintana, the recently appointed national commissioner in charge of searching for the disappeared. So this number, 40 thousand people, it's only the official number we have. Reporter: So it could be double or triple that? That would be my guess. We know that lots of disappearances are not taken to authorities. They are afraid of the same authorities in some cases, or the organized crime, the cartels. Reporter: Quintana is refreshingly blunt for a government official. How have we gotten to the point in this country where it's mothers who have to bear the injury of losing their children and then have to endure the insult of being forced to go then do the search themselves? Well, I think it's because the government, they don't care much about who has been disappeared. There is this stigma in Mexico that we have, we also have to fight that if someone is disappeared, it's because they were doing something and they were involved in something, which is not true. Reporter: We've been following the case of Lucy Diaz, and she's perhaps the most prominent mom involved in the searches. And it appears that there are very clear leads in this case that are just not being followed, and I wonder if somebody like Lucy can't get the police to do anything, how can anybody expect any action on their case? Mexican justice system is -- it's very poor, specifically regarding to people that that are disappeared. We only have 30 decisions -- judicial decisions in Mexico. Reporter: So sentencing somebody for making somebody else disappear -- Yeah. Reporter: That's only happened 30 times? Yeah. Reporter: So essentially, in this country, you can kill somebody, bury them in a shallow grave, and get away with it? Well, I'm a public servant, but I would have to say yes. Reporter: With the official in charge of searching for the missing failing to provide much hope, we decide to go all the way to the top, to the president of Mexico. Would you commit here and now to using your power to taking a look at her case to see if you can move it forward? When we come back.
This transcript has been automatically generated and may not be 100% accurate.