Shocking footage shows 51 people, mostly from Central America, cramped into the back of the transit lorry.
It comes just a week after the White House released similar footage showing 35 migrants crossing into Arizona.
The group, from Ecuador, Honduras, Guatemala, El Salvador and Nicaragua, are now being held in custody in Mexico's National Migration Institute (INM), government officials said.
They will be returned to their home countries.
It comes as Mexican officials have captured more than 200 migrants hidden in trucks over the past two days, including dozens spotted by a large X-ray scanner huddled in secret compartments.
The country is cracking down on migration under pressure from the US.
An additional 228 hidden migrants were found in a routine search of a soft drink transportation truck in the southern state of Chiapas on Monday, Mexico's security ministry said in a statement.
The apprehensions come weeks after the appointment of hard-charging former prisons chief Francisco Garduno as the new head of Mexico's immigration authority, the National Migration Institute (INM).
Under Garduno, the agency has made a number of high-profile captures of migrants smuggled in commercial vehicles. The weekend Garduno took office, INM found 800 people in four trucks in the eastern state of Veracruz.
Mexico's stepped-up efforts to stop record flows of mainly Guatemalans, Hondurans and El Salvadorans reaching the United States follow a June 7 deal under which Mexico averted tariffs threatened by President Donald Trump with a promise to use security forces to intercept more undocumented migrants.
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 migrants from Guatemala, Honduras, El Salvador, Nicaragua and Ecuador - 21 of whom were minors - are now in the custody of the INM, the security ministry said late on Sunday, adding they will be returned to their home countries.
The truck, its 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, the ministry added.
Mexico's Foreign Minister Marcelo Ebrard said the attorney general has about 11 open investigations into migrant smugglers.
'It is our strategic objective to end the impunity for human traffickers,' Ebrard said at a news conference on Monday.
The video comes as the White House has shared a startling X-Ray of a produce truck, which was scanned at an Arizona border crossing and revealed 35 migrants hiding inside.
The image was posted on the White House Instagram account on Wednesday night.
It shows adults standing between rows of produce and one lying on the floor.
The government said the people were being kept in the back with no air conditioning by a people smuggler.
'Last night, 12 children, a pregnant woman, a convicted felon, and 19 other illegal aliens were found locked in a produce truck at a checkpoint in Arizona.
'The driver, charged with human smuggling, kept the refrigeration off, so they were trapped inside where it was over 97 degrees with no way out.
'THANK YOU to our heroic Border Patrol agents, whose vigilance caught this smuggler and potentially saved lives,' the post said.
In a series of other photographs, the migrants are seen sitting on the road while agents search the truck.
In another, an agent is seen tending to one of the young toddlers found inside.
The crisis at the border has become a hot topic in recent presidential nominee debates.
Democrats have flocked to detention centers around the country, demanding to inspect conditions, and some have crossed into Mexico to help asylum seekers who have been reported return to the US.
Trump maintains the situation is not as dire in the facilities in the US as is claimed.
The Dail Mail
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