The Mexican government says some 150 Central American migrants, including 62 children, were found inside the back of a tractor trailer this weekend.
Mexican federal police and immigration officials discovered the migrants while searching trucks at a highway checkpoint.
Police say the majority of the migrants came from Guatemala, others were from El Salvador, Honduras, and Nicaragua.
Tens of thousands of Central Americans fleeing violence and poverty in their homelands try to pass through Mexico to the United States every year.
The majority, through the Rio Grande Valley.