The health insurance giant has called a new report from WSJ “misinformation,” but investors may not be so sure. Shares were down about 9% early Friday. UnitedHealth Group, America’s largest insurer, is facing yet another crisis.

The U.S. Justice Department is investigating UnitedHealth's Medicare billing practices, the Wall Street Journal reported on Friday, while the health insurer said it was unaware of any new probe underway.

The US Justice Department has been investigating UnitedHealth Group Inc.’s Medicare billing practices, a person familiar with the matter said. The company’s stock fell sharply. Most Read from BloombergTrump Targets $128 Billion California High-Speed Rail ProjectTrump to Halt NY Congestion Pricing by Terminating ApprovalTrump Asserts Power Over NYC,