46 migrants found dead in abandoned trailer in San Antonio, Texas

Forty-six people were found dead in a sweltering tractor-trailer that was abandoned on a remote back road in San Antonio in what marked the latest tragedy to claim the lives of migrants smuggled across the border from Mexico to the U.S. Sixteen people were hospitalized, including four children.

A city worker heard a cry for help from the truck shortly before 6 p.m. Monday and discovered the gruesome scene, police Chief William McManus said. Hours later, body bags lay spread on the ground near the trailer as a grim symbol of the calamity.

San Antonio Mayor Ron Nirenberg said the 46 who died had "families who were likely trying to find a better life."

"This is nothing short of a horrific human tragedy," Nirenberg said.

It's among the deadliest tragedies to have claimed thousands of lives of people attempting to cross the U.S. border from Mexico in recent decades. Ten migrants died in 2017 after being trapped inside a truck that was parked at a Walmart in San Antonio. In 2003, 19 migrants were found in a sweltering truck southeast of San Antonio.

The home countries of the immigrants and how long they were abandoned on the side of the road was not immediately known.

South Texas has long been the busiest area for illegal border crossings. Migrants ride in vehicles though Border Patrol checkpoints to San Antonio, the closest major city, from which point they disperse across the United States.

A city worker at the scene on a remote back road in southwest San Antonio was alerted to the situation by a cry for help, McManus said. Officers arrived to find a body on the ground outside the trailer and a partially opened gate to the trailer, he said.

Hours later, body bags lay spread on the ground near the trailer. Bodies still remained inside.

Of the 16 taken to hospitals with heat-related illnesses, 12 were adults and four were children, said fire Chief Charles Hood. The patients were hot to the touch and dehydrated, and no water was found in the trailer, he said.

"They were suffering from heat stroke and exhaustion," Hood said. "It was a refrigerated tractor-trailer, but there was no visible working AC unit on that rig."

Those in the trailer were part of a presumed migrant smuggling attempt into the United States, and the investigation was being led by U.S. Homeland Security Investigations, McManus said.

Three people were taken into custody, but it was unclear if they were definitively connected with human trafficking, McManus said.

Big rigs emerged as a popular smuggling method in the early 1990s amid a surge in U.S. border enforcement in San Diego and El Paso, Texas, which were then the busiest corridors for illegal crossings.