At least 46 migrants found dead in Texas truck

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

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.

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

The city's Police Chief William McManus said 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 there is now a federal investigation and that three people were in custody following the incident, though their involvement is not yet clear.

A spokesperson for U.S. Immigration and Customs Enforcement 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 illegal migration across the U.S.-Mexico border. The issue has proven difficult for U.S. President Joe Biden, a Democrat who has pledged to reverse some of the hardline immigration policies of his Republican predecessor Donald Trump. Republicans have criticized Biden's border strategy ahead of the midterm congressional elections in November.

Police Chief McManus said this was the largest incident of its kind in the city. In July 2017, ten migrants died after being transported in a tractor-trailer that was discovered by San Antonio police in a Wal-Mart parking lot.