Mexico City (CNN) -- Soldiers looking for drugs in the southern border state of Chiapas instead found 140 migrants inside a tractor-trailer.
The truck was stopped and searched at a routine checkpoint over the weekend, according to the Defense Ministry, known as SEDENA.
Two men were detained in connection to the migrants, who SEDENA said were from Central America.
Chiapas, which borders Guatemala, is a major crossing point for Central American immigrants heading north.
Mexican authorities apprehended about 25,000 illegal immigrants there last year, according to the country's National Migration Institute.
In May, authorities said they found and detained more than 500 illegal immigrants from Central America and Asia who were crammed inside two tractor-trailers heading toward the United States.