Image copyright EPA Image caption Some 600 migrants were discovered at the head of a truck
Mexican authorities have arrested 18 people found hidden in two trailers loaded with fresh produce heading to northern United States.
The arrests occurred on Wednesday, when police stopped the tractor-trailers in Veracruz state, the office of attorney general said.
Authorities found around 600 migrants, some of them as young as 14, stowed in the trailers.
It is the second incident in recent days involving Mexicans trying to cross into the US illegally.
Rescue workers on Tuesday saved more than 100 migrants who had managed to get off a packed cargo ship in Texas.
A spokeswoman for the state health department said all of the migrants had been taken to the hospital after being found below deck.
‘Modern slavery’
The migrants smuggled to the US by the Veracruz trafficker were taken to a hospital in the city of Progreso, the Veracruz state public safety director said.
Ms Efrain Arias Leyva told Reuters news agency that two migrants suffered life-threatening conditions, with one suffering from a heart attack.
It is not known how long the migrants were involved in the smuggling.
Veracruz state said the operation to get the detained men and women arrested was one of the largest in recent years in the state.
The prosecution office has launched an investigation, but has yet to make any official charges.
“What happened in Veracruz is a new level of impunity that they are creating here in Mexico,” Jose Miguel Vivanco, director of Human Rights Watch’s Americas division, told the AFP news agency.
“What they are doing is one of the most shocking forms of modern slavery,” he said.
He added that he hoped the arrest would be the start of a “new era” in the investigation.
On Monday, the interior ministry of neighbouring Tamaulipas state said there had been 30 such arrests in recent days.