By Krupskaia Alís and Rafael Romo, CNN

(CNN) -- Luz María Telumbre still clings to the hope that her son is alive, even though many people in her town believe that he's gone forever.

"Very few people are still supporting us," Telumbre recently told CNN in her adobe house in the town of Tixtla, a rural area in the coastal Mexican state of Guerrero, where she was making corn tortillas on the griddle to sell them and help her husband Clemente Rodríguez make ends meet.

"Six years is a long time," she says.

That's how long it's been since Telumbre last saw her son, Christian Alfonso Rodríguez. Affectionately known as "Lolo", Rodríguez was then a 19-year-old college student. He had just began his first semester at the Raúl Isidro Burgos School for Teachers in the nearby town of Ayotzinapa.

In late September 2014, he joined a group of about 100 students from his college traveling in two buses they had commandeered to stage a protest in Iguala, a city two hours away by car.

Sometime between the night of September 26, 2014 and the following morning, the buses were intercepted by local police and the federal military forces in Iguala, according to authorities at the time. The bullet-riddled buses could later be seen in the city's streets. The windows had been shattered by the bullets and there was blood everywhere. And 43 students, including Christian Alfonso Rodríguez, had gone missing.

Other students who were on the buses later spoke of a night of horror. Armed police officers and soldiers stopped the buses and suddenly opened fire, they said. The ones who were not immediately shot had dropped to the floor to save their lives while yelling at the top of their lungs, pleading with the officers to cease fire. A student told CNN he saw one of his closest friends get shot in the head.

CNN reached out to the Mexican Attorney General's Office and the Mexican Department of Defense about any inquiries into the alleged role of the military and police. So far there has been no answer.

In October 2015, then-Mexican Defense Secretary Salvador Cienfuegos Zepeda rejected any involvement by members of the army under his command, though soldiers of the 27th Battalion -- which serves the region where the students disappeared -- were questioned by the Attorney General's Office at the time.

In spite of repeated pleas over the years, protests, marches, meetings with government officials and several investigations by two different administrations and international forensic experts, the parents of the 43 missing students feel they are no closer to knowing what happened to their children today than they were six years ago.

"There are [human rights and legal aid] organizations that are still supporting us [parents], but there are now fewer of them. There are fewer of them because too much time has gone by and they're probably getting tired," Telumbre said.

There were initially dozens of arrests, but to date no one has been convicted in connection with the disappearance of the students. The motive remains a mystery, and speculation about government corruption at the highest levels has run rampant in Mexico in the years that have passed.

During the administration of former President Enrique Peña Nieto, who was in power when the disappearance occurred, investigators first said the students had been murdered by a drug gang in cahoots with corrupt police and military officials, because they thought the students belonged to rival gangs.

Jesús Murillo Karam, who was the Attorney General when the students disappeared, said in November 2014 that the young men were abducted on orders of the local mayor, turned over to a gang that killed them, burned their bodies in Cocula landfill and tossed the remains into a nearby river.

But some elements of that version, described by the Peña Nieto government as "the historical truth," were rejected in 2015 by a group of independent forensic experts who were hired by the Inter-American Human Rights Commission to investigate the case. In particular, the report refuted the landfill theory.

The administration of current President Andrés Manuel López Obrador, who took office in December 2018, also rejected his predecessor's efforts and announced a new investigation that would "start again from square one".

"This is a state issue. We're committed to solving the case and we're making progress towards that goal. It's a commitment we have with the parents [of the missing students] and the Mexican people," President Andrés Manuel López Obrador said about the case on September 23.

CNN got in touch with the Mexican Attorney General's Office and the country's Department of Defense to inquire whether there's any investigation related to the Ayotzinapa case involving military personnel, but as of this writing, there has been no response.

In early July this year, Mexican authorities announced they had identified the remains of one of the 43 students who went missing.

Thanks to a forensic DNA analysis conducted by the University of Innsbruck in Austria, investigators were able to tie a bone fragment to Telumbre's son, according to the Mexican Attorney General's Office and the Forensic Anthropology Team from Argentina, which has conducted its own, independent investigation in the case.

Both Telumbre and her husband Clemente Rodríguez, father of the missing student, say they respect the finding and the efforts to find the truth about the missing -- but that it doesn't change their belief that their son, somehow, somewhere is still alive.

"What we have always said is that what they found is not what remained of my son. It's a very small fragment, weighing two grams, from my son's right foot. People may think I'm crazy, but I know my son is watching me and, to me, he's not dead. I know that, even with a foot missing, he will come back. I will not rest until the very last line of investigation is exhausted and until I finally know what truly happened to him," Telumbre said.

Christian Alfonso Rodríguez was the second student to be identified. In December 2014, less than three months after they went missing, the Forensic Anthropology Team from Argentina told the parents of Alexander Mora Venancio that a single bone fragment found inside a trash bag in a river near the landfill had been used to identify their own 19-year-old son. https://www.cnn.com/2014/12/06/world/americas/mexico-missing-student-id/index.html

Yet Clemente Rodríguez is still clinging to one of the early theories about what happened to the 43 missing students: that they were kidnapped and taken to a remote place in Guerrero's mountains where they're still being held, possibly as forced laborers.

"I have even told the current government that if they find out about a possible site where they might be, I don't know, anywhere in the mountains, I will go somehow and try to find him. I would give my life for my son if necessary," Rodríguez told CNN.