46 Dead Migrants, 16 Survivors Found Inside Trailer Truck In Texas

San Antonio, Texas -- At least 46 people believed to be migrants were found dead inside a tractor-trailer Monday.

The deceased people were discovered inside the trailer of an 18-wheeler truck on Quintana Road just before 6 p.m., the New York Post reported, citing San Antonio Police Chief William McManus.

All 46, composed of men and women from teens to young adults, died from heat stroke and heat exhaustion as the trailer had no air conditioning and water, according to San Antonio Fire Department Chief Charles Hood.

Temperatures in San Antonio reportedly reached a high of 103 degrees Fahrenheit Monday amid an ongoing heat wave.

First responders helped 16 survivors, including four minors, Hood said, per KSAT 12.

The survivors were reportedly hot to the touch upon being discovered. They were taken to local hospitals for their heat-related injuries.

They were treated in University Health, Central Methodist, Central Baptist and CHRISTUS Santa Rosa Westover Hills, according to the Mexican Consulate.

All the victims were believed to have been undocumented migrants who crossed into the United States illegally from Mexico. At least two of the people in the trailer were from Guatemala, said Marcelo Ebrard, the Mexican secretary of external relations.

The suspected migrants were discovered after a nearby worker heard a cry for help and found the trailer with its doors partially open and saw bodies inside, police said.

Monday's discovery was the largest mass casualty event in San Antonio, according to authorities.

"It's tragic. They had families... and were likely trying to find a better life. It’s nothing short of a horrific human tragedy," San Antonio Mayor Ron Nirenberg said.

"We hope that those responsible for putting these people through such inhumane conditions are prosecuted to the fullest extent of the law," he added.

Three people have been taken into custody, according to McManus, but he was unsure if they were connected to the incident.

Efforts to ensure that everyone in the trailer truck was accounted for would be stretched into the days ahead, a report by KENS 5 said.

The Department of Homeland Security has since taken over the investigation.

"Details will be released as they are available, the criminal investigation remains ongoing," the agency's principal investigative arm, Homeland Security Investigations, said in a statement.

The number of migrants apprehended while entering the U.S. through the country's southern border has risen to the highest level in decades, according to The New York Times.