Federal authorities are investigating whether UT Southwestern Medical Center and Dallas-based Parkland Memorial Hospital committed fraud by falsely billing Medicare and Medicaid for patient care. The probe already has identified millions of dollars in potential fraud in the government health insurance programs for the elderly, disabled, and poor. Investigators are focusing on whether UT Southwestern billed the government for services that faculty physicians did not actually provide while working at Parkland. A key question is whether faculty physicians properly supervised residents, the Dallas Morning News reports.