Officials have been stunned by a “surge” of unaccompanied children crossing into the United States.

Although some have traveled from as far away as Sri Lanka and Tanzania, the bulk are minors from Mexico and from Central America’s so-called Northern Triangle—Guatemala, Honduras, and El Salvador, which together account for 74 percent of the surge. Long plagued by instability and unrest, these countries have grown especially dangerous in recent years: Honduras imploded following a military coup in 2009 and now has the world’s highest murder rate. El Salvador has the second-highest, despite the 2012 gang truce between Mara Salvatrucha and Barrio 18. Guatemala, new territory for the Zetas cartel, has the fifth-highest murder rate; meanwhile, the cost of tortillas has doubled as corn prices have skyrocketed due to increased American ethanol production (Guatemala imports half of its corn) and the conversion of farmland to sugarcane and oil palm for biofuel.