Soldiers discovered 140 undocumented Central American migrants hidden inside a truck crossing the southern border state of Chiapas, Mexico's defense department said Monday.

The migrants were found during a routine inspection at a checkpoint set up near the town of Tonala as part of operations targeting organized crime, the department said in a statement.

Two people were arrested for transporting the Central Americans "in conditions that put their physical well-being at risk," while the migrants were turned over to Mexican immigration authorities for repatriation, the statement said.

An estimated 140,000 Central Americans enter Mexico each year on their way to the United States, walking part of the way or riding aboard freight trains, buses and cargo trucks.

The trek is fraught with danger, with criminals and corrupt Mexican officials preying on the migrants, who often pay traffickers as much as $10,000 to get them to the United States.