The disclosure sent UNH shares tumbling 4.7%, reflecting investor unease with the ongoing troubles with the healthcare stock. This admission adds to a string of challenges that have battered the company, with its stock now trading 56% below its 52-week high.

UnitedHealth (UNH) shares inched down on Thursday after the insurance giant confirmed the U.S. Justice Department is investigating its Medicare billing practices. The DOJ is investigating whether the NYSE-listed firm artificially inflated Medicare reimbursements by overstating or exaggerating patient health conditions.

UnitedHealth shares tumbled Thursday after the health insurance giant confirmed that it’s the subject of a Department of Justice investigation. Monitor these key chart levels.

UnitedHealth confirmed it was under investigation by the Department of Justice and said it was complying with both criminal and civil requests.

The healthcare conglomerate said it was complying with requests from the agency after reaching out following media reports.