Authorities in the southern U.S. state of Texas found 46 migrants dead inside a tractor-trailer truck Monday.

San Antonio Fire Chief Charles Hood told reporters another 16 people were taken to the hospital for treatment of heat-related injuries, including four children.

The truck was found next to railroad tracks in a remote area on the southern outskirts of San Antonio. High temperatures in the city topped 39 degrees Celsius (103 degrees Fahrenheit) Monday with high humidity.

San Antonio police said they could not yet say where the people inside the truck were from. Federal authorities were in charge of the investigation.

Mexican Foreign Secretary Marcelo Ebrard tweeted that, according to the Mexican consul who went to the area, there were two Guatemalans among those taken to the hospital.

Ebrard said the trailer had U.S. license plates, and that the incident was highly likely the work of human traffickers.

San Antonio Mayor Ron Nirenberg called the situation “nothing short of a horrific human tragedy.”

“It’s tragic,” Nirenberg told reporters. “There are, that we know of, 46 individuals who are no longer with us who had families, who were likely trying to find a better life.”

In 2017, 10 migrants died after being trapped in a tractor-trailer that San Antonio police discovered in a Walmart parking lot. The driver of that truck was sentenced to life in prison for his role in the smuggling operation.

Some information for this report came from The Associated Press and Reuters.
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