The Obama administration failed to protect thousands of Central American children who have flooded across the U.S. border since 2011, leaving them vulnerable to traffickers and to abuses at the hands of government-approved caretakers, a Senate investigation has found. The Office of Refugee Resettlement, an agency of the Department of Health and Human Services, failed to do proper background checks of adults who claimed the children, allowed sponsors to take custody of multiple unrelated children, and regularly placed children in homes without visiting the locations, according to a 56-page investigative report released Thursday. And once the children left federally funded...