In this aerial view, members of law enforcement investigate a tractor trailer in San Antonio, Texas on June 27, 2022. Photo: AFP

The bodies of 46 dead migrants were discovered inside a tractor-trailer on Monday in San Antonio, Texas, city officials said, in one of the deadliest recent incidents of human smuggling along the US-Mexico border.

A San Antonio Fire Department official said they found "stacks of bodies" and no signs of water in the truck, which was found next to railroad tracks in a remote area on the city's southern outskirts.

Sixteen other people found inside the trailer were transported to hospitals for heat stroke and exhaustion, including four minors, but no children were among the dead, the department said.

"The patients that we saw were hot to the touch, they were suffering from heat stroke, exhaustion," San Antonio Fire Chief Charles Hood told a news conference. "It was a refrigerated tractor-trailer but there was no visible working A/C unit on that rig."

Temperatures in San Antonio, which is about 160 miles (250 kilometers) from the Mexican border, swelled to a high of 103 F (39.4 C) on Monday with high humidity.

The city's Police Chief William McManus said that a person who works in a nearby building heard a cry for help and came out to investigate. The worker found the trailer doors partially opened and looked inside and found a number of dead bodies.

McManus said this was the largest incident of its kind in the city and said three people were in custody following the incident, though their involvement is not yet clear.

A spokesperson for US Immigration and Customs Enforcement (ICE) said that its Homeland Security Investigations division was investigating "an alleged human smuggling event" in coordination with local police.

The deaths once again highlight the challenge of controlling migrant crossings at the US-Mexico border, which have reached record highs.

The issue has proven difficult for US President Joe Biden, a Democrat who came into office in January 2021 pledging to reverse some of the hard-line immigration policies of his Republican predecessor Donald Trump. Republicans have criticized Biden's border strategy ahead of the midterm congressional elections in November.

Mexico's Foreign Minister Marcelo Ebrard called the suffocation of the migrants in the truck the "tragedy in Texas" on Twitter and said consular officials would go to the hospitals where victims had been taken to help "however possible."

A spokesperson for the Honduran foreign ministry told Reuters the country's consulates in Houston and Dallas would be investigating the incident. Ebrard said two Guatemalans were hospitalized and Guatemala's foreign ministry said on Twitter that consular officials were going to the hospital "to verify if there are two Guatemalan minors there and what condition they are in."

Reuters