The truck at the centre of a human-smuggling attempt that left 53 people dead had passed through an inland border checkpoint, a US official has revealed.
The truck went through the checkpoint on Interstate 35, 42 kilometres northeast of the border city of Laredo, Texas.
The official said there were 73 people in the truck when it was discovered on Monday in San Antonio, including the 53 who died. It was unclear if agents stopped the driver for questioning at the inland checkpoint or if the truck went through unimpeded.
The disclosure brings new attention to whether the roughly 110 inland highway checkpoints along the Mexican and Canadian borders are sufficiently effective at spotting people in cars and trucks who enter the United States illegally.
Texas state police also announced they would operate their own inland checkpoints on the orders of Governor Greg Abbott, who considers the Biden administration's efforts insufficient.
Meanwhile Homero Zamorano Jr., 45, the alleged driver of the truck, made his initial appearance in San Antonio federal court.
Judge Elizabeth Chestney appointed a federal public defender for Zamorano as well as a second attorney since the smuggling charge he faces carries a possible death sentence. She scheduled a hearing next week to determine if he is eligible for bail.
It remained unclear just how long the migrants were in the trailer on the sweltering day and whether having their mobile phones confiscated by the smugglers before being placed inside contributed to the extremely high death toll.
Jose Santos Bueso of El Progreso, Honduras said his daughter, 37-year-old Jazmin Nayarith Bueso Nunez, told him in their last conversation that she was in Laredo, that the smugglers were going to take their phones and she would not be able to communicate for a time.
The US Supreme Court ruled in 1976 that Border Patrol agents may stop vehicles at inland checkpoints for brief questioning without a warrant, even if there is no reason to believe that they are carrying people in the country illegally. Still, the practice has galvanised immigration advocates and civil libertarians who consider checkpoints ripe for racial profiling and abuse of authority.
Border Patrol officials call the checkpoints an imperfect but effective second line of defence after the border, acknowledging that agents must balance law enforcement interests with disrupting legitimate commerce and travel.
US Rep. Henry Cuellar, who drives through the checkpoint almost weekly, said investigators believe the migrants boarded the truck in or around Laredo, though that is unconfirmed. That would be consistent with smuggling patterns: migrants cross the border on foot and hide in a house or in shrubbery on US soil before getting picked up and taken to the nearest major city.
Australian Associated Press
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