The Wall Street Journal says the U.S. Justice Department in recent months has launched an investigation into UnitedHealth Group’s billing practices to see if the company fraudulently used diagnosis data to trigger extra Medicare Advantage payments.

UnitedHealth Group (UNH) is under fire over its Medicare billing practices. The Wall Street Journal reported Friday that the U.S. Department of Justice (DOJ) has launched a civil fraud investigation into how the company records diagnoses that lead to extra payments for its Medicare Advantage plans.