Mexican authorities have discovered 343 migrants and refugees, including 103 unaccompanied minors, in an abandoned freight truck container on the side of a highway.

The National Immigration Institute (INM) said on Monday the trailer was found in the steamy Gulf coast state of Veracruz. It was on a route often used by smugglers to bring people from southeastern Mexico to the United States border.

The people were in good health and it was unclear why the driver fled, authorities said.

Most of the children were from Guatemala. Migrants who make it to the US frequently pay smugglers to bring their children afterwards.

The institute said the adults were mainly from Guatemala, Honduras, El Salvador and Ecuador.

The children will be put into the custody of Veracruz’s family services system while the others will be processed to determine their legal status in Mexico, INM said.

People have been found dead inside abandoned freight containers in the past.

Record levels
The conditions in the container illustrated the increasing sophistication of smugglers. The trailer had fans and ventilation ports cut in the roof and the people wore colour-coded bracelets, apparently to identify them as smugglers’ clients.

Trucks are one of the most dangerous methods used by people smugglers to transport undocumented migrants through Mexico to the US.

Last June, more than 50 people died after they were abandoned in a scorching hot tractor-trailer truck in San Antonio, Texas.

In December 2021, 56 US-bound migrants from Central America were killed and dozens injured when the truck they were travelling in overturned in southern Mexico.

Movement across the US-Mexico border reached record levels in 2022 with US Border Patrol documenting 2,378,944 “encounters” in the region.