The Justice Department is probing diagnoses and practices that triggered extra payments to UnitedHealth’s Medicare Advantage plans, people familiar with the matter say.

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 Wall Street Journal says the Justice Department in recent months has launched a new investigation into UnitedHealth Group’s billing practices as a civil fraud investigation looks at the use of diagnosis data to trigger extra payments to the company’s Medicare Advantage plans.