SAN ANTONIO, texas - In the chaotic minutes after dozens of migrants were found dead inside a semitrailer 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 and three other men 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. Federal prosecutors said two of the suspects, including the driver, face charges that carry a potential sentence of life in prison or the death penalty if convicted.

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. Among the dead were 27 people 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.

Hard to identify

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 have to be shared and matched by the governments involved.

Javier Flores Lopez's family was waiting to find out whether he was on the truck. He had returned home to see his wife and three small children in southern Mexico and was going back to Ohio where his father and a brother live and where he worked in construction. He is now among the missing and his cousin Jose Luis Vasquez Guzman is hospitalized in San Antonio, the family said.

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.

Magdalena Tepaz, center, and Manuel de Jesus Tulul, right, parents of Wilmer Tulul, wait for the start of a community meeting in Tzucubal, Guatemala, June 29, 2022. Wilmer and his cousin Pascual, both 13, were among the dead discovered inside a semitrailer on the edge of San Antonio, Texas, June 27.

While it's not clear when or where the migrants boarded the truck bound for San Antonio, Department of Homeland Security investigators believe it was on U.S. soil, near or in Laredo, Texas, U.S. Representative Henry Cuellar told The Associated Press.

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.

Families Fret Over Fate of Migrants Trapped in Texas Truck

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 Governor 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.

Driver from suburban Houston

Federal prosecutors identified the driver as Homero Zamorano Jr., 45, who was charged with smuggling resulting in death. Zamorano lives in suburban Houston and is originally from the Texas border city of Brownsville, according to the U.S. Attorney's Office in San Antonio.

He faces the most serious charges along with Christian Martinez, 28, who is accused of conspiracy and allegedly communicated with Zamorano about transporting the migrants.

Martinez was arrested in East Texas and will be transported to San Antonio. Zamorano was scheduled to have his first court appearance Thursday. It was not immediately known if either suspect had an attorney.

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.

Migrants typically pay $8,000 to $10,000 to be taken across the border, loaded into a semitrailer and driven to San Antonio, where they transfer to smaller vehicles for their final destinations across the United States, said Craig Larrabee, acting special agent in charge of Homeland Security Investigations in San Antonio.

The death count from Monday's tragedy in San Antonio was the highest ever from a smuggling attempt in the U.S., he said. Ten people died in 2017 after being trapped inside a truck parked at a San Antonio Walmart. In 2003, the bodies of 19 migrants were found in a truck southeast of the city.

Temperatures in San Antonio on Monday approached 100 degrees Fahrenheit (38 degrees Celsius), and those taken to the hospital were hot to the touch and dehydrated, authorities said.