Forty-six people have been found dead inside a lorry in Texas, USA in temperatures approaching 100 degrees Fahrenheit (38 Celsius).
The suspected migrants were in a truck that appeared to have no air conditioning or water and were “hot to the touch”, San Antonio fire chief Charles Hood told reporters.
Officials said they found “stacks of bodies” inside the vehicle, which was close to railway lines in a remote area on the city’s southern outskirts.
A further 16 people, including four children, were taken to hospital with heat stroke and exhaustion.
No children were among the dead.
Following the incident, Texas governor Greg Abbott tweeted that “these deaths are on Biden”, adding: “They are the result of his deadly open border policies.”
A rule introduced under the Trump administration in March 2020 during the coronavirus pandemic and kept by Biden denies migrants – largely from Mexico, Guatemala, Honduras and El Salvador – a chance to seek asylum. But is thought to encourage repeat attempts because there are no legal consequences for getting caught.
Since the law was introduced, people crossing the border illegally have been expelled more than two million times.
Biden has reversed some of his predecessor’s immigration policies including halting construction of the border wall, and reaffirming protections for some migrants.
Beto O’Rourke, the Democratic candidate running against Mr Abbott, called for urgent action to “dismantle human smuggling rings and replace them with expanded avenues for legal migration”.
In May, a record 239,000 undocumented migrants were detained crossing into the country from Mexico.
“It was a refrigerated tractor-trailer but there was no visible working A/C unit on that rig,” Mr Hood said.
“We are not supposed to open up a truck and see stacks of bodies. Nobody comes to work for that.”
Someone who works in a nearby building decided to investigate after hearing a cry for help, San Antonio police chief William McManus said.
Finding the trailer doors partially open they looked inside and discovered a number of dead bodies.
Hours later, body bags were seen spread on the ground.
It is the city’s largest incident of its kind and three people are in custody, Mr McManus added.
The Interstate 35 highway, on which the truck was found, runs through San Antonio from the Mexican border and is a popular route for people smugglers.
A spokesperson for US Immigration and Customs Enforcement (ICE) said its homeland security investigations division was looking into an “alleged human smuggling event” in coordination with local police.
San Antonio’s mayor, Ron Nirenberg, said the discovery was “nothing short of a human tragedy”, adding: “Our job is not to ask why. Our job is to ask how we can help.”
The Secretary of Foreign Affairs for Mexico, Marcel Ebrard, said a consul is on its way to the neighbourhood and at least two of those in hospital were from Guatemala.
“Tragedy in Texas. Reportedly suffocated in trailer box,” he tweeted.
