U.S. border agents arrested about 8 percent fewer people in July than in June. But the number of migrant families detained remained nearly constant. The numbers were released by the Department of Homeland Security. Reuters reports 31,303 were arrested July, compared to 34,095 in June. Of those detained about 4,000 were children crossing the U.S.-Mexico border alone. That's compared to about 5,100 children in June.