Forty-six people were found dead in a strangling tractor-trailer that was abandoned on a remote road in San Antonio in southern U.S. Texas, marking the latest tragedy to claim the lives of migrants smuggled across the border from Mexico into the United States, AP writes.

Sixteen people have been hospitalized. Fire Chief Charles Hood says of the 16 people taken to hospitals for heat-related reasons, 12 were adults and four were children. He said the patients were hot to the touch and dehydrated, and no water was found in the truck. "They suffered from heat stroke and exhaustion," Hood said.

The heat is a serious hazard, especially when the temperature inside the vehicles can rise dramatically. The weather in the San Antonio area on Monday was mostly cloudy, but temperatures were approaching 38 degrees.

San Antonio Mayor Ron Nirenberg said the 46 dead had "families who were probably trying to get a better life." "This is nothing short of a terrible human tragedy," Nirenberg said.

Three people have been taken into custody, but it is unclear whether they were definitively linked to human trafficking.

It is one of the deadliest tragedies to claim thousands of lives trying to cross the U.S. border from Mexico in decades. Ten migrants died in 2017 after being trapped inside a truck parked outside a Walmart in San Antonio. In 2003, 19 migrants were found strangled in a truck southeast of San Antonio.