The Justice Department is investigating UnitedHealth Group for possible criminal Medicare fraud, people familiar with the matter said. The healthcare-fraud unit of the Justice Department’s criminal division is overseeing the investigation,

The reported probe adds to a string of recent setbacks that have erased more than half, or over $300 billion, from its market value since November.

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.