Forty-six people were found dead and 16 others were taken to hospital after being found inside a tractor-trailer rig on Monday on a remote back road in south-west San Antonio, Texas officials have said.

The discovery may prove to be the deadliest tragedy among thousands who have died attempting to cross the USborder from Mexico in recent decades.

A city worker at the scene was alerted by a cry for help shortly before 6pm Monday, police chief William McManus said. Officers arrived to find a body on the ground outside the trailer and a partially opened gate to the trailer, he said.

Sixteen were taken to hospital with heat-related illnesses, of which 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.



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

Those in the trailer were part of a presumed smuggling attempt for those attempting to enter the United States, and the investigation was being led by US Homeland Security Investigations, McManus said.

Mexican foreign minister Marcelo Ebrard said the Mexican consul was en route to the site Monday.

Ebrard said in a tweet that the victims’ nationalities were still unknown.
The Mexican general consulate in San Antonio said on Twitter that it would provide aid to any Mexicans involved in the incident. It also said consul general Ruben Minutti was on his way to the scene.

Governor Greg Abbott said in a tweet the people were found in the back of a truck and blamed the deaths on political division and how borders are secured.

The city has been the scene of previous migrant deaths. Ten people died in 2017 after being trapped inside a truck that was parked at a Walmart in San Antonio. In 2003, 19 others were found in a sweltering truck south-east of San Antonio.

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

Before that, people paid small fees to mom-and-pop operators to get them across a largely unguarded border. As crossing became exponentially more difficult after the 2001 terror attacks in the US, individuals were led through more dangerous terrain and paid thousands of dollars more.

Heat poses a serious danger, because temperatures can rise steeply inside vehicles. Weather in the San Antonio area was mostly cloudy Monday, but temperatures approached 100F (38C).

Photos posted to Twitter by a KSAT reporter showed multiple police vehicles and ambulances surrounding a large truck.

Associated Press and Reuters contributed to this story.