SAN ANTONIO -- In the minutes after dozens of migrants were found dead inside a tractor-trailer sweltering under the Texas sun, the driver tried to slip away by pretending to be one of the survivors, a Mexican immigration official said Wednesday.
The driver, along with two other men from Mexico, remained in custody as the investigation continued into the tragedy that killed 53 people -- the nation's deadliest smuggling episode on the U.S.-Mexico border.
Two more people died Wednesday as the death toll slowly climbed since the discovery of 46 bodies Monday at the scene near auto salvage yards on the edge of San Antonio.
The truck had been packed with 67 people, and the dead included 27 from Mexico, 14 from Honduras, seven from Guatemala and two from El Salvador, said Francisco Garduno, chief of Mexico's National Immigration Institute.
Officials had potential identifications on 37 of the victims as of Wednesday, pending verification with authorities in other countries, according to the Bexar County Medical Examiner's Office. Forty of the victims were male, it said.
Identifying the dead has been challenging because some were found without identification documents and in one case a stolen ID. Remote villages where some of the migrants came from in Mexico and Central America have no phone service to reach family members and fingerprint data has to be shared and matched by the governments involved.
The tragedy occurred at a time when huge numbers of migrants have been coming to the U.S., many of them taking perilous risks to cross swift rivers and canals and scorching desert landscapes. Migrants were stopped nearly 240,000 times in May, up by one-third from a year ago.
While it's not clear when or where the migrants boarded the truck bound for San Antonio, Homeland Security investigators believe it was on U.S. soil, near or in Laredo, Texas, U.S. Rep. Henry Cuellar told reporters.
The truck went through a Border Patrol checkpoint northeast of Laredo on Interstate 35 on Monday, Cuellar and Mexican officials confirmed. It was registered in Alamo, Texas, but had fake plates and logos, Garduno said.
Officials in Mexico also released a surveillance photo showing the driver smiling at the checkpoint during the more than two-hour trip to San Antonio.
Republican Texas Gov. Greg Abbott said Wednesday that state troopers would set up additional truck checkpoints on highways, but he did not say how many. In April, Abbott gridlocked the 1,200-mile Texas border for a week by requiring every truck entering the state to undergo additional inspections as part of his ongoing fight with the Biden administration over immigration policy.
Authorities were looking into whether the truck had mechanical problems when it was left next to a railroad track. The driver was apprehended after trying to disguise himself as one of the migrants, Garduno said.
Some of the more than a dozen people transported to hospitals were found suffering from brain damage and internal bleeding, according to Ruben Minutti, the Mexico consul general in San Antonio.
Information for this article was contributed by Paul J. Weber, Elliot Spagat, Julie Watson, Tammy Webber, Edgar H. Clemente, Sonia D. Perez and Marlon Gonzalez of The Associated Press.