In recent days, Mexico has been cracking down on migrant caravans, arresting and deporting more of the immigrants moving through the country toward the United States.

But in Central America, KCBS Radio Political Reporter Doug Sovern found out that the Mexican government was already getting tough on those migrants, even as President Trump was complaining the country wasn't doing enough.

Here is Part 4 of this week's special 5-part series, "A Desperate Frontier: Death And Dreams In El Salvador."