U.S. investigators are asking some of the nation's largest banks to tighten their policies on accepting cash deposits in an effort to choke off the financial channels of human smugglers. The requests, which have prompted at least one bank to review its rules for depositing cash into consumer accounts, come amidst a recent influx of illegal border crossings by Central Americans into the United States, including nearly 60,000 unsupervised children, most of who are from violence-ravaged Honduras, Guatemala and El Salvador. In one prong of its response to the migratory spike, the U.S. Department of Homeland Security has ramped up...