U.S. Was Warned of Migrant Child Labor, but ‘Didn’t Want to Hear It’

In the spring of 2021, Linda Brandmiller was working at an arena in San Antonio that had been converted into an emergency shelter for migrant children. Thousands of boys were sleeping on cots as the Biden administration grappled with a record number of minors crossing into the United States without their parents.

Ms. Brandmiller’s job was to help vet sponsors, and she had been trained to look for possible trafficking. In her first week, two cases jumped out: One man told her he was sponsoring three boys to employ them...