BUZZ-UnitedHealth falls on report of DOJ's probe into co's Medicare billing practices

Shares of healthcare conglomerate UnitedHealth UNH.N fall 8.7% to $458.7 premarket

U.S. Department of Justice launched investigation into co's Medicare billing practices in recent months, Wall Street Journal reports, citing people familiar with the matter

DOJ's new civil fraud investigation is examining UNH's practices for recording diagnoses that trigger extra payments to its Medicare Advantage plans, according to the newspaper

Stock has fallen ~5% in last 12 months