The death toll from a human trafficking incident on Monday in which migrants suffered under extreme Texas heat inside a truck rose to 50 on Tuesday, Mexican President Andres Manuel Lopez Obrador said.

The migrants died inside a tractor-trailer in San Antonio, Texas, where temperatures swelled to a high of 103 degrees Fahrenheit (39.4 degrees Celsius). It was one of the most deadly recent incidents of human smuggling along the U.S.-Mexico border.

Local and U.S. authorities said there were no signs of water and no visible working air conditioning inside the truck.

"I want to offer my condolences to the relatives of this catastrophe," Lopez Obrador said.

Some 22 Mexicans, seven Guatemalans and two Hondurans were identified among the dead, Mexico Foreign Minister Marcelo Ebrard said on Twitter on Tuesday. There was no information on the nationality of the other 19, Mexican officials said.

The U.S. Immigration and Customs Enforcement (ICE) said that its Homeland Security Investigations division was conducting a criminal investigation into "an alleged human smuggling event" in coordination with local police.

Sixteen other people were transported to hospitals for heat stroke and exhaustion, including four minors, but no children were among the dead, the San Antonio Fire Department said.

A spokesman for the Honduran foreign ministry told Reuters that the country's consulates in Houston and Dallas would be investigating the incident.

Immigration officials from Mexico are also assisting the families of the victims and the transfer of the bodies, Lopez Obrador said.

The city's police chief, William McManus, on Monday said a person who works in a nearby building heard a cry for help and came out to investigate. The worker found the trailer doors partially opened and looked inside and found a number of dead bodies.

McManus said this was the largest incident of its kind in the city and said three people were in custody following the incident, although their involvement was not clear.

"The people that are responsible for subjecting other people to these conditions should be prosecuted to the fullest extent of the law," San Antonio Mayor Ron Nirenberg said during an interview on CNN on Tuesday.

RECORD CROSSINGS

The deaths once again highlight the challenge of controlling migrant crossings at the U.S.-Mexico border, which have reached record highs.

Lopez Obrador on Tuesday said he will meet with U.S. President Joe Biden in Washington on July 12 to discuss migration.

The issue has proven difficult for Biden, a Democrat who came into office in January 2021 pledging to reverse some of the hardline immigration policies of his Republican predecessor, Donald Trump. Republicans have criticized Biden's border strategy ahead of the midterm congressional elections in November.

White House press secretary Karine Jean-Pierre said that Biden has been briefed and will continue to get updates on the situation.

"Far too many lives have been lost to this dangerous journey. We will continue to take action to disrupt human smuggling networks, which have no regard for lives. They exploit and endanger in order to make a profit," she said aboard Air Force One.

The I-35 highway near where the truck was found runs through San Antonio from the Mexican border and is a popular smuggling corridor because of the large volume of truck traffic, according to Jack Staton, a former senior official with ICE's investigative unit who retired in December.

In July 2017, 10 migrants died after being transported in a tractor-trailer that was discovered by San Antonio police in a Wal-Mart parking lot. The driver, James Matthew Bradley, Jr., was sentenced the following year to life in prison for his role in the smuggling operation.