In another video of the X-ray-assisted detention released by Mexican authorities, an official approached the cargo vehicle at night to open the door to one of the crates. Sobs emerged from the otherwise-quiet container while he identified himself as a police officer and asked if migrants were in good health.
The truck, the driver, and 225,000 Mexican pesos ($12,000) in cash found in the vehicle are now in police custody, and will be subject to investigation, INM said.
Mexico's Foreign Minister Marcelo Ebrard said the attorney general has about 11 open investigations into migrant smugglers.
Authorities seized about $3.7 million in undeclared U.S. currency Sunday after searching an abandoned boat on the coast of Puerto Rico.
U.S. Customs and Border Protection first spotted the boat on the water with no lights leaving Fajardo and heading east toward the U.S. Virgin Islands, the agency said in a news release.
Suddenly the boat turned around and made its way back to Fajardo, stopping at the entrance of Rio Fajardo.
Border Patrol, Border Protection, Air and Marine Operations and DEA agents followed the boat and found people unloading duffel bags. The unidentified occupants immediately abandoned their cargo and fled.