A group of migrants from China surrendered to a Border Patrol agent in remote Southern California as gusts of wind drowned the hum of high-voltage power lines, joining others from Ecuador, Brazil, Colombia and elsewhere in a desert campsite with shelters made from tree branches.

Their arrival Wednesday was another sign that agents have become overwhelmed in recent days by asylum-seekers on parts of the U.S. border with Mexico. In tiny Eagle Pass, Texas, nearly 6,000 migrants crossed from Mexico in to the U.S. in two days, prompting authorities to close one of the town’s two official border crossings so those agents could instead help with the influx. Border crossings have closed recently for similar reasons in San Diego and El Paso, Texas.