It seems Mexico is trying to make it much more difficult for illegal aliens from Central and South America to cross its territory on their way to the United States. The Financial Times reports:
Even without Mr Trump’s fortress frontier, Mexico finds itself under increasing pressure to stem the migrant tide near its source — its own southern border.
“Mexico has become a wall for migrants,” said Sister Magdalena Silva, co-ordinator of Cafemin, a privately run shelter in Mexico City that takes in refugee families, including Rosa’s. “The current policy is to arrest migrants to stop them from getting to the US border.”
The UN estimates 400,000 Central Americans cross illegally into Mexico each year and as many as half of those are fleeing violence. The majority are quickly deported back to dangerous homes.
Unlike in the US, Mexico has broadened asylum laws to recognise that fleeing violence of the kind practised by the street gangs of Honduras and El Salvador can classify someone as a refugee. But the odds are still stacked against asylum seekers: Mexico deported a record 175,000 Central Americans last year, up 68 per cent from the previous year and nearly two-and-a-half times the number deported by the US.
The US is coy about its role in Mexico’s crackdown but is sending $75m in equipment and training to help stop Central Americans from crossing illegally into Mexico. Hosting Mr Trump two weeks ago, President Enrique Peña Nieto said that “making Mexico’s border with our friends and neighbours in Central America more secure is of vital importance for Mexico and the US”.
There's more at the link (which may disappear behind a paywall).
Sounds to me as if Mexico is saying to Central and South Americans, in so many words, "Hey - illegal entry into the USA is for our people. You lot find your own salvation somewhere else!"