The death toll of the unlawful migrants discovered abandoned in the back of a sweltering tractor-trailer on Monday in San Antonio has risen to 53 as of Wednesday morning, according to a news report.

As reported by The Dallas Express, first responders said they initially found 46 bodies inside the vehicle upon arrival at the scene. San Antonio Fire Department Chief Charles Hood said Monday that 16 people were found alive inside the truck and were taken to local hospitals.

Meanwhile, a Texas trucking firm claims that one of its trucks appears to have been “cloned” as part of the alleged illegal smuggling activity.

Felipe Betancourt Sr., the owner of Betancourt Trucking and Harvesting in Alamo, said the unlawful migrants were in a Volvo semi-truck that had been copied to look like one of his company’s commercial vehicles, the San Antonio Express-News reports. Betancourt said whoever obtained the vehicle copied everything from the color to the federal and state transportation department identifying numbers.

“Ours is sitting right here,” Felipe Betancourt Jr., son of the company’s owner, told the Express-News. “My truck doesn’t have a window on the side like the one in San Antonio. … That one in San Antonio is not our trailer.”

It is not uncommon for human smuggling groups and cartels to replicate legitimate vehicles to use in illegal border crossings, the newspaper reported.

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Mexico’s National Immigration Institute Chief, Francisco Garduno, said on Wednesday that the semi-truck’s driver was allegedly captured after pretending he was one of the migrants being transported. He was identified as Homero Zamorano, 45.

A law enforcement official said Zamorano appeared to be high on meth and was taken to a local hospital, according to the newspaper report.

Zamorano was reported to have a lengthy criminal history and now faces charges of human smuggling.

Two other men have also been charged in connection with the incident. The semi-truck was traced to a home in Bexar County, where police surveilled the two men. A search warrant was obtained for the house, where police reportedly found firearms.

The two men, Juan Francisco D’Luna-Bilbao and Juan Claudio D’Luna-Mendez, were arrested on suspicion of possessing firearms while being in the country unlawfully.

The Associated Press reported that this incident was the nation’s deadliest smuggling episode on the U.S.-Mexico border.

In a statement released by the Bexar County Medical Examiner’s Office, officials said that 37 of the victims had been tentatively identified as of Wednesday, but they have not been publicly identified. Among the dead were 40 males and 13 females, and some were reportedly children.

U.S. President Joe Biden called the incident “horrifying and heartbreaking” in a White House news release. He vowed that his administration would “continue to do everything possible to stop human smugglers and traffickers from taking advantage of people who are seeking to enter the United States between ports of entry.”

The statement further read: “While we are still learning all the facts about what happened, and the Department of Homeland Security has the lead for the investigation, initial reports are that this tragedy was caused by smugglers or human traffickers who have no regard for the lives they endanger and exploit to make a profit. This incident underscores the need to go after the multi-billion dollar criminal smuggling industry preying on migrants and leading to far too many innocent deaths.”

In April, Texas Gov. Greg Abbott ordered state police to inspect every commercial vehicle entering Texas through a port of entry, claiming that the intensive measure was necessary because the Biden administration failed to secure the border. Following the discovery of those dead, Abbott placed the blame directly on the Biden administration.

“At Least 42 People Found Dead Inside Truck Carrying Migrants In Texas,” he tweeted. “These deaths are on Biden. They are a result of his deadly open border policies. They show the deadly consequences of his refusal to enforce the law.”