FALFURRIAS, TX - JULY 25:  U.S. Border Patrol agents detain undocumented immigrants after a foot chase on July 25, 2014 near Falfurrias, Texas. Tens of thousands of illegal immigrants have crossed into the U.S. this year, causing a humanitarian crisis on the U.S.-Mexico border. Texas' Rio Grande Valley has become the epicenter of the latest immigrant crisis, as more Central Americans have crossed illegally from Mexico into that sector than any other stretch of America's 1,933 mile border with Mexico.  (Photo by John Moore/Getty Images)