JUAREZ, Mexico (AP) — Mexicans are increasingly the face of asylum in the United States, replacing Central Americans who dominated last year's caravan and a surge of families that brought border arrests to a 13-year-high in May.

Border arrests plummeted as U.S. policies targeting asylum have taken hold. But Mexicans are exempt by virtue of being a neighboring country.

U.S. Customs and Border Protection figures show fewer Mexicans are crossing, but the drop in Central Americans is much sharper, making Mexicans the biggest part of the mix. Mexicans arrested or stopped at the border fell 22% from May to August, but border crossers from Central American countries were down from 63% to 81%.

It is unclear precisely what is driving the change, perhaps a mix of U.S. policies and violence in Mexico.