Mexican officials said an American citizen was among those who survived triple-digit temperatures in the back of an abandoned trailer in Texas that killed 51 migrants and was among the smuggling suspects. 

The migrants were discovered Monday evening in the outskirts of San Antonio and the Mexican consul was en route to the site. The driver of the truck and two others have been arrested, U.S. Rep. Henry Cuellar of Texas told The Associated Press.

He said the truck had passed through a Border Patrol checkpoint northeast of Laredo, Texas, on Interstate 35. He did not know if migrants were inside the truck when it cleared the checkpoint.

Investigators traced the truck’s registration to a residence in San Antonio and detained two men from Mexico for possession of weapons, according to criminal complaints filed by the U.S. attorney’s office. 

BIDEN ADMIN SIGNS FIVE-YEAR CONTRACT TO HOUSE MIGRANT KIDS AT FORMER NORTH CAROLINA SCHOOL

San Antonio migrants

Police work the scene where dozens of people were found dead in a semitrailer in a remote area in southwestern San Antonio on Monday. (AP)

The complaints did not make any specific allegations related to the deaths.

Many of the dead were males. The dozen or so who survived were taken to hospitals. Five of the people who died were children. 

Authorities do not know the home countries of all the migrants. By Tuesday, medical examiners had had potentially identified 34 of the victims, said Bexar County Commissioner Rebeca Clay-Flores.

Among the dead, 27 are believed to be of Mexican origin based on documents they were carrying, according to said Rubén Minutti, Mexico consul general in San Antonio. Several survivors were in critical condition with injuries such as brain damage and internal bleeding, he said.

At least seven of the dead migrants were from Guatemala and two from Honduras, Roberto Velasco Álvarez, head of the North America department in Mexico’s Foreign Relations Department, said on Twitter. About 30 people had reached out to the Mexican Consulate looking for loved ones, the officials said.

The identity of the U.S. citizen who reportedly survived was not released.  

CLICK HERE TO GET THE FOX NEWS APP

The Associated Press contributed this report.