The U.S. Department of Justice is carrying out a criminal investigation into UnitedHealth Group for possible Medicare fraud, the Wall Street Journal reported on Wednesday. UnitedHealth said it had not been notified by the DOJ about the "supposed criminal investigation reported,

UnitedHealth Group shares fell nearly 6% in premarket trading on Thursday, after the Wall Street Journal reported that the U.S. Department of Justice was investigating the company for potential Medicare fraud.