The 136 migrants, from Honduras, Guatemala, El Salvador and Nicaragua, were rescued in the violent southeastern state of Veracruz after 24 hours in temperatures above 38 Celsius, Mexico’s migration institute INM said.

Tens of thousands of Central Americans fleeing violence and poverty in their homelands aim to pass through Mexico to the United States every year, often transported by human traffickers who subject them to perilous conditions.

More than 800 Central American migrants have been found in truck trailers or safe houses in Mexico so far this year, according to a government document seen by Reuters.

Border apprehensions fell when US President Donald Trump took office last year and vowed to stamp out illegal immigration, suggesting fewer crossing attempts, but have picked up in recent months.

The migrants in Veracruz were discovered by federal police and migration agents who heard cries for help from within the truck, which had been abandoned near a freeway.

Authorities said they counted 49 minors among the group, 13 of whom were traveling alone and will receive aid to apply for refugee status in Mexico. The adults, as well as the accompanied children, will be sent back to their home countries.

Last month, 103 Central Americans, including 36 minors, were rescued from an abandoned truck in the violent northern state of Tamaulipas, where migrants often attempt illegal border crossings.

In July, 10 people died after a truck stuffed with more than 100 Guatemalan and Mexican migrants was abandoned in a Texas parking lot.