At least 46 people have been found dead in a truck that was believed to be carrying migrants from Mexico to Texas.
Local officials said the bodies were discovered in a sweltering 18-wheel truck that was next to rail tracks in a remote area on the outskirts of San Antonio on Monday.
Police Chief William McManus said a city worker heard a cry for help from the truck shortly before 6pm and found the gruesome scene.
Sixteen people, including four children, were taken to local hospitals. The patients were exhausted and "hot to the touch", San Antonio Fire Chief Charles Hood said, adding that there were no signs of water onboard the truck.
“They were suffering from heat stroke and exhaustion,” Mr Hood said.
“It was a refrigerated tractor-trailer, but there was no visible working AC unit on that rig.”
Officials found "stacks of bodies" but no children were believed to be among the dead.
Texas has been at the centre of a new wave of migration. The Rio Grande Valley Border Patrol, which usually sees more migrant arrivals than any of the agency’s nine US-Mexico border sectors, reported having encountered 100 groups of 100 migrants or more, and a total of more than 15,000 people, since the fiscal year 2022 began in October 2021.
It came as President Joe Biden pledged to move away from the hardline immigration policy of his predecessor Donald Trump. His administration has instructed agents to focus on deporting those people in the US illegally who have committed dangerous crimes, as well as targeting employers exploiting migrants instead of raiding workplaces to look for people working illegally.
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,” he said.
San Antonio police said on Monday evening three people were in custody.
Temperatures have been scorching in San Antonio in recent days and climbed to 39.4C (103F) on Monday, with high humidity – and the temperature in a trailer packed with people is likely to have greatly exceeded this.
At Least 42 People Found Dead Inside Truck Carrying Migrants In Texas.
These deaths are on Biden.
They are a result of his deadly open border policies.
They show the deadly consequences of his refusal to enforce the law. https://t.co/8KG3iAwlEk
— Greg Abbott (@GregAbbott_TX) June 28, 2022
Images posted to Twitter by local media showed police vehicles and ambulances surrounding a large truck.
Big rigs are a popular smuggling method for people trying to get across the Mexican border into the United States.
Greg Abbott, Texas's Republican governor, was quick to blame the deaths on Joe Biden and pointed his finger at the US President's "open border policies", tweeting:
Beto O'Rourke, the Democratic candidate who is running against Mr Abbott in November's election, called for action to "dismantle human smuggling rings and replace them with expanded avenues for legal migration".
Thousands of people have died attempting to cross the US border from Mexico.
The incident is the largest of its kind in San Antonio, which has witnessed a number of similar incidents.
Ten migrants died in 2017 after being trapped inside a truck that was parked at a Walmart. In 2003, 19 migrants were found in a sweltering truck southeast of the city.
Mexican Foreign Minister Marcelo Ebrard said the Mexican consul was en route to the site in San Antonio, which is about 160 miles (250 km) from the Mexican border.
Mr 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, if there were any. He added that two of the people taken to hospital were Guatemalan.