A Mexican official says Mexican, Guatemalan, and Honduran citizens are among the dead found in the back of a Texas truck

• Citizens from Mexico, Guatemala and Honduras were found among the dozens dead inside a truck in Texas, a Mexican official said.
• The death toll in the incident rose from 46 to 51 as of Tuesday afternoon, said an ICE spokesperson.

The death toll from an apparent human smuggling incident in which dozens of bodies of migrants were found inside a scorching hot tractor-trailer in Texas rose to 51 on Tuesday — and victims include citizens from Mexico, Guatemala, and Honduras, US and Mexican officials said.

Twenty-two Mexicans, seven Guatemalans, and two Hondurans were found among the dead in the abandoned big rig that was discovered in a remote area in San Antonio on Monday, Mexican Foreign Minister Marcelo Ebrard said in a tweet on Tuesday, citing information he said was provided by US authorities.

"The others are yet to be identified. We are in mourning. Huge tragedy," Ebrard tweeted. "Mexico joins investigations in the US, coordinated with DHS."

Homeland Security Investigations, a branch of US Immigration and Customs Enforcement, is handling the investigation into the matter.

An ICE spokesperson confirmed to Insider that the death toll from incident jumped to 51 from 46 as of Tuesday afternoon.

The federal agency said that HSI responded to a call from the San Antonio Police Department on Monday night "in reference to an alleged human smuggling event involving a tractor-trailer."

"HSI San Antonio has initiated an investigation with support of SAPD," ICE said. "Details will be released as they are available, the criminal investigation remains ongoing."

The ICE spokesperson said that HSI detained three people "believed to be part of the smuggling conspiracy."

Two Mexican nationals who were in the US illegally — Juan Claudio D'Luna-Mendez and Juan Francisco D'Luna-Bilbao — were federally charged on Tuesday in connection to the incident.

They were each charged with "possession of a weapon by an alien illegally in the United States," according to criminal complaints filed in US District Court for the Western District of Texas.

The men were arrested during two separate vehicle stops after the registration plate on the truck where the bodies were discovered led authorities to a San Antonio residence, according to the court documents.

Authorities found several weapons inside the bedrooms of D'Luna-Mendez and D'Luna-Bilbao, as well as inside the truck D'Luna-Mendez was driving at the time, the criminal complaints say.

Law enforcement officials learned of the truck deaths — believed to be one of the worst migrant death cases near the southern border — after a San Antonio, Texas, worker made the grim discovery inside the truck after hearing a cry for help Monday night.

Local authorities said Monday at a press conference that 46 bodies were found and that 16 people, including four minors, were hospitalized.

"The patients that we saw were hot to the touch," San Antonio Fire Chief Charles Hood said. "They were suffering from heat stroke, heat exhaustion."

Five people were taken to San Antonio's Baptist Medical Center where three of them later died, a hospital spokesperson told Insider on Tuesday.

The two people hospitalized there remain in critical condition, according to the spokesperson.

At Monday's press conference, San Antonio Mayor Ron Nirenberg said, "The plight of migrants seeking refuge is always a humanitarian crisis, but tonight we are dealing with a horrific human tragedy."

Nirenberg called the incident "tragic."

The mayor said that the the victims "had families who were likely trying to find a better life."