PHOENIX (AP) — Three Mexican migrants have died in the Sonoran Desert in Arizona near the U.S.-Mexico border as high temperatures soar well into the triple digits across parts of the Southwest.

The U.S. Border Patrol reported Friday that the bodies of two men, ages 44 and 18, and a 17-year-old girl were found in the desert early Wednesday in an area called Sheep Mountain, which is in southwestern Arizona on the Barry M. Goldwater Range, a remote military training area near the Cabeza Prieta National Wildlife Refuge.

A rescue beacon for migrants to call for help had been activated, setting off a search by land and air. Another member of the group of four was found alive. The bodies were taken to the Pima County Medical Examiner’s Office for autopsies. The Mexican Consulate was notified.

The high temperatures this week in Arizona’s lower deserts and Phoenix this week have been averaging 110 to 115 degrees Fahrenheit (43 to 46 C) as the region swelters through an excessive heat watch that extends into the Lower Colorado Valley and southeastern California. In Las Vegas, where the high was expected to hit 103 degrees F (39 C) on Friday, the National Weather Service said hotter than normal temperatures in the triple digits are expected over the next week because of a ridge of high pressure over the western United States.

Those kinds of temperatures can spell danger for people who are outside in the sun for hours.

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“The terrain along the border is extreme, the relentless summer heat is severe, and remote areas where smugglers bring migrants is unforgiving,” said Deputy Border Chief Patrol Agent Justin De La Torre of the agency’s Tucson Sector. ”Far too many people who made the decision to place their lives into the hands of the criminal organizations have died of dehydration, and heat stroke.”

In Maricopa County, which encompasses Phoenix, there have been six heat-related deaths reported so far this year. Another 111 deaths are being investigated for possible heat causes. In Pima County, home to Tucson, the medical examiner’s office reports that there have been eight heat-related deaths confirmed so far this year for that county and several small rural ones it handles.

Maricopa County public health officials confirm there were a staggering 645 heat-related deaths last year in the jurisdiction of about 4.5 million people — more than 50% higher than 2022 and another consecutive annual record in arid metro Phoenix.

That report alarmed officials in America’s hottest big metro, raising concerns about how to better protect vulnerable groups from the blistering heat.