Ever since a caravan of Central American migrants started heading north from Southern Mexico in early April, President Trump has used the occasion to accuse the Mexican government of doing nothing to prevent migrants from reaching the United States.

But that isn’t true. Mexico has actually done a lot in the past several years, with some success — but also some unintended consequences.

In the summer of 2014, when record numbers of Central American children and families were apprehended at the U.S.-Mexico border, the Obama administration pressured Mexico to stop the migrant flow closer to the source: at its own southern border with Guatemala.

Mexico readily complied, deploying unprecedented numbers of immigration agents, police, and military to shut down migrant routes, primarily in the southernmost state of Chiapas. By some measures, the so-called Southern Border Program was successful: In its first two years, immigration arrests in Mexico shot up by 85 percent, according to an analysis by the Washington Office on Latin America.

Now, four years later, it’s clear that the Southern Border Program has created more problems than it’s solved. Rather than stopping migrants, Mexico's immigration crackdown has just pushed them to new and more dangerous routes, where they’re vulnerable to predatory criminals who rob them — or much worse.

Those migrants who are apprehended often wind up stuck for months in southern Mexico while they await for their cases to be processed. Many apply for asylum in Mexico, but even they, in many cases, want papers only so they can proceed on their journeys north undisturbed. As long as there's intense violence, poverty, and political instability in their home countries, the migrants will keep coming.

This segment originally aired June 7, 2018 on VICE News Tonight on HBO.