(NewsNation) — The four years between when Rogelio Madera Cervantes went missing after he left Jalisco, Mexico and the identification of his remains were a “nightmare” for his family.

After he went missing, his family searched for him along the U.S.-Mexico border, checking detention centers and morgues in Tijuana and Nogales, Arizona, but to no avail.

Somewhere along his journey across the border, he was separated from the group he was traveling with, and died in the desert near Yuma, Arizona.

“It’s one thing to lose someone who dies along the U.S.-Mexico border… that is a traumatic experience,” said Jason De León, executive director of The Colibrí Center for Human Rights, a non-profit based in Tuscon, Arizona. “But I think it’s 10 times worse to not know what has happened to that loved one. To not know whether or not they’re dead or alive.”

When his remains were found in the desert about three years later, the Colibrí Center helped make an identification for his family through DNA testing.

The Colibrí Center’s work began in 2006 and by 2017, it began compiling DNA samples it collected into a database they can use to compare against a separate database of unidentified remains, which are collected and maintained by the Pima County Office of the Medical Examiner.

Workers collect the DNA themselves, sometimes traveling internationally to places like Honduras to find family members willing to offer a comparative sample.

The process can take years.

Cervantes’ family lost contact with him in July 2013 after he set out with a “coyote,” another term for a human smuggler, in Arizona.

They later learned Cervantes wasn’t well during the trip and couldn’t keep up with the group, said Mayra Ibarra, who is married to Cervantes’ nephew.

“(The coyote) said that he left him in (a Native American) reservation or community in Yuma, Arizona,” Ibarra said.

Then in 2015, Ibarra heard about Colibrí Center for Human Rights during a Univision news report. She was put in touch with a “gentle girl” whom Ibarra said immediately relieved some of her anxiety.

“My heart told me that they would help us,” Ibarra said. “It was a long process but we were always in touch.”

Colibrí’s services are free to families of missing persons but come at a cost for the non-profit, which operates on donations and public funding.

There was pain and grief when Cervantes’ sister received the phone call confirming the DNA match, but it was tempered with the relief of closure.

After so long, the family was relieved to have him back. All those years, “They hoped to find him, dead or alive,” Ibarra said.

Closing a case is bittersweet, but De León considers it a win. Altogether, Colibrí has made 261 identifications for families that would otherwise be left in the dark.

But it’s a challenging process, and those 200-plus cases represent only about 6% of all the missing person reports the center has received — reports that span 14 countries and 43 U.S. states.

It can be a sobering statistic considering the Pima County Medical Examiner’s Office is in possession of about 1,192 unidentified remains.

But De León knows the families behind those numbers and is driven by their stories.

“There’s nobody else doing this,” De León said. “If we were to shut the doors, there’s no longer a phone number to call, no longer someone to manage to case manage.”

The consulate of each country is responsible for arranging deceased migrants’ repatriation, and the specifics of those practices vary.

For the families of people who lost their lives crossing the border, DNA is often the most promising tool for identification. Desert conditions can be brutal, leading to quickly deteriorating remains, but it’s a deterrent for those willing to navigate their way through miles of hot, oppressive climate.

“The entire Sonoran Desert is just one giant graveyard,” De León said.

U.S. Customs and Border Patrol (CBP) has set up rescue beacons and placards, which allow migrants to call for help and easily identify their location.

“Smuggling organizations are abandoning migrants in remote and dangerous areas, leading to a rise in the number of rescues but also tragically a rise in the number of deaths,” a CBP spokesperson said.

Border Patrol recorded a record number of migrant deaths in the fiscal year 2021 — about 600. Border agents helped rescue about 13,000 others.

For those that don’t make it, CBP has some measures in place such as its Missing Migrant Program, which also works to match remains with DNA.

But a recent review by the Government Accountability Office found that Border Patrol’s reports of migrant deaths were inconsistent and recommended better coordination with outside agencies. CBP agreed to those recommendations and has already begun initiating them, according to the report.

The Colibrí Center’s work is possible in part because of its partnership with the Pima County Medical Examiner’s Office. But that level of cooperation isn’t guaranteed across the country and isn’t common along the border, according to the non-profit.

Colibrí takes reports of missing people elsewhere, including Texas, California, New Mexico, and Mexico.

“Right now there’s over 1,500 unidentified sets of remains from Arizona,” De León said. “And that only includes people that had been found.”