UnitedHealth Group has said it has not been notified by the Department of Justice of a reported criminal investigation. The Wall Street Journal reported on Wednesday that the firm is facing a DOJ investigation for possible Medicare fraud,

Shares of UnitedHealth Group tumbled 16% in intraday trading Thursday, leading S&P 500 decliners, on a report that the U.S. Department of Justice is investigating the embattled health insurance provider for possible criminal Medicare fraud.