Una manta que se supone que perteneciΓ³ a un cruzador de fronteras se encuentra cerca de la base de las montaΓ±as Baboquivari, al oeste de Tucson.

 Josh Galemore / Arizona Daily Star

The known death toll among migrants crossing the harsh terrain along Arizona’s border with Mexico reached 227 last year, the highest yearly total on record, according to recently released statistics.

The total for 2020 was a 58% increase over the 144 sets of human remains recovered in 2019, according to records from the Pima County Office of the Medical Examiner and the humanitarian aid group Humane Borders.

Since the crisis of migrants dying in large numbers at the Arizona-Mexico border began two decades ago, the medical examiner has documented the deaths of nearly 3,400 migrants. However, those records only account for remains that were found. The actual total of migrant deaths is unknown.

The rise in migrant deaths last year was a reversal of a fairly steady decrease in recent years, said Dr. Greg Hess, chief medical examiner for Pima County.

The new international border wall near Yuma and San Luis, Arizona, on October 6, 2020. Video by Kelly Presnell / Arizona Daily Star

Before 2020, the highest number of remains found in a single year came in 2010, when 224 sets of remains were found, according to an online database maintained by Humane Borders. The database includes remains from Pima, Santa Cruz, and Cochise counties, which are handled by the Pima County medical examiner, as well as a small number of remains found in Maricopa County.

The exceedingly hot and dry weather last summer likely contributed to more migrants dying as they crossed the desert, Hess said.

None of the deaths were linked to coronavirus infections, Hess said. Where cause of death could be determined, the most common cause was exposure to the elements, particularly hyperthermia, medical examiner records show.

Medical examiner records for 2020 show nearly half of the human remains were found less than three months after the person died. Others belonged to people who may have died years ago.

So far, about 70 sets of remains have been identified. Most belonged to migrants from Mexico, along with 11 from Guatemala, two from Honduras and two from Colombia, according to medical examiner records.

In one incident from August, which the National Weather Service in Tucson said was the hottest month on record, a 35-year-old woman from Mexico crossed the border with a group near the Baboquivari Mountains southwest of Tucson. She couldn’t keep up with the group and someone in the group called her family in Mexico to tell them she had fallen behind. Her family contacted humanitarian aid workers in Tucson, who then called the Pima County Sheriff’s Department, according to a deputy’s incident report.

She couldn’t be found at the time, but several weeks later, agents with the Border Patrol’s search and rescue team found her body as they looked for a group of migrants near the Border Patrol checkpoint on Arizona 86. A canine with the search and rescue team picked up her scent and guided the agents to her body. In the phone that a sheriff’s deputy found a few feet from her body, the deputy saw she had several unread text messages, voice calls, and notifications on WhatsApp of people trying to reach her.

She was one of 24 migrants who died in the corridor that runs north from Sasabe, along the Baboquivari Mountains, and continues along the western flank of Tucson into Maricopa County.

Most of the human remains were found in the desert and mountains west and southwest of Tucson, including 96 sets of remains on the Tohono O’odham Nation. Another 18 sets of remains were found in the corridors that run north from Nogales and Patagonia to Tucson. Cochise County saw 19 sets of remains found. The locations for three sets of remains were not listed. Two were found on the Barry M. Goldwater Bombing Range.

β€œWhat concerns me when there is that remarkable spike in bodies is people are still coming over, but they’re not traveling in easily accessible areas,” said Dan Abbott, a volunteer with Humane Borders who helps supply water stations for migrants near Ajo.

Abbott has not seen a large increase in the use of the water stations, β€œwhich suggests to me that people are having to go even further west, which is really inhospitable country,” he said.

Medical examiner records show 65 sets of remains were found in the area near Ajo and the Cabeza Prieta National Wildlife Refuge to the west.

The total for 2020 could change slightly as the Medical Examiner’s Office tries to identify human remains, which at times can lead to the realization that what appeared to be two different sets of remains actually belong to one person, Hess said.

The medical examiner uses a number of factors to determine whether remains belong to migrants, Hess said, such as finding carpeted shoes, camouflage clothing, foreign currency and other items common to migrants in the desert. Other factors include the remains not being buried and not being connected to any missing-persons reports.

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Contact reporter Curt Prendergast at 573-4224 or cprendergast@tucson.com or on Twitter @CurtTucsonStar