Federal and Tennessee authorities are investigating a report of child abuse at a facility in Chattanooga used to house unaccompanied minors who were picked up by Border Patrol agents along the U.S.-Mexico border, according to the head of the state’s Department of Children’s Services (DCS). While providing scant details, Jennifer Nichols, the head of the agency, told Tennessee lawmakers during a hearing on Wednesday that a teenage boy at the facility told the Department of Children’s Services about the alleged abuse. The teen boy, who wasn’t identified, said he wasn’t the victim but had witnessed abuse, Nichols said during a hearing with the Government Operations Joint Subcommittee on Education, Health, and General Welfare. Now, the FBI, Department of Homeland Security (DHS), and state officials are investigating the matter, she added. Nichols didn’t disclose the nature of the allegations made by the teen. Six children being housed in the facility, she said, were selected …