MEXICO CITY Mexican authorities found 129 migrants, mostly from Guatemala, crowded into a truck trailer in the eastern state of Veracruz, the National Migration Institute (INM) said in a statement on Saturday.

The migrants were crammed into a trailer in the midst of a heat wave in Mexico, where higher-than-normal temperatures have topped 45C (113F) in several states, including Veracruz, where the operation took place.

Immigration agents in late May had uncovered another 175 migrants further south, mainly from Central America, in Chiapas state. Another 300 people were stopped at a checkpoint in Veracruz in March.

Migrants fleeing violence and poverty in Latin America frequently pay smugglers in an attempt to pass through Mexico bound for the U.S. Some are forced to cross areas rife with drug violence, making them vulnerable to organized crime.

Among the travelers found on Friday were adults from Guatemala, Honduras, India and El Salvador, and 19 unaccompanied minors, the migration institute said. It added that the children will be put under state guardianship, while the others will be processed to determine their legal status in Mexico. Four suspected traffickers were arrested in the operation.

On Friday the commissioner of the INM, Francisco Garduño, had met with Guatemalan officials to discuss reparations for the victims of a deadly March fire in a migrant detention center in Mexico that claimed 39 lives, the INM said in a separate statement.

(Reporting by Lucinda Elliott and Aida Pelaez-Fernandez; Editing by Franklin Paul)