A water station for immigrants containing sealed jugs of fresh water sits along a fence line near a roadway in rural Jim Hogg County, Texas, on July 25.

HEBBRONVILLE, Texas — As one of the worst heat waves on record set in across much of the southern United States this summer, authorities and activists in South Texas found themselves embroiled in a mystery in this arid region near the border with Mexico.

Barrels of life-saving water that a human rights group had strategically placed for wayward migrants traveling on foot had vanished.

Usually, they are hard to miss. Labeled with the word “AGUA” painted in white, capital letters and standing about waist-high, the 55-gallon (208-liter), blue drums stand out against the scrub and grass, turned from green to a sundried brown.

Summer temperatures can climb to 110 degrees Fahrenheit (43.3 degrees Celsius) in Texas’ sparsely populated Jim Hogg County, with its vast, inhospitable ranchlands. Migrants — and sometimes human smugglers — take a route through this county to try to circumvent a Border Patrol checkpoint on a busier highway about 30 miles (48 kilometers) to the east. More than 60 miles (96 kilometers) from the U.S.-Mexico border, it can take several days to walk there for migrants who may have already spent weeks crossing mountains and desert and avoiding cartel violence.

“We don’t have the luxury of losing time in what we do,” said Ruben Garza’s, an investigator with the Jim Hogg Sheriff’s Office. Tears streamed down his face as he recalled helping locate a missing migrant man who became overheated in the brush, called for help but died just moments after his rescue.

Exact counts of those who die are difficult to determine because deaths often go unreported. The U.N. International Organization for Migration estimates almost 3,000 migrants have died crossing from Mexico to the U.S. by drowning in Rio Grande, or because of lack of shelter, food or water.

Walter almost gave up crossing the Mexican desert. Then a fellow migrant carried him
MY UNSUNG HERO FROM HIDDEN BRAIN
Walter almost gave up crossing the Mexican desert. Then a fellow migrant carried him
Humanitarian groups started placing water for migrants in spots on the U.S. side of the border with Mexico in the 1990s after authorities began finding bodies of those who succumbed to the harsh conditions.

John Meza volunteers with the South Texas Human Rights Center in Jim Hogg County, where the population of about 5,000 people is spread over 1,100 square miles (2,850 square kilometers) — larger than the state of Rhode Island. He restocks the stations with gallon jugs of water, trims away overgrown grass, and ensures the GPS coordinates are still visible on the underside of the barrel lids.