In a securities filing, UnitedHealth said it has begun complying with formal criminal and civil requests from the DOJ.

UnitedHealth Group confirmed that its Medicare Advantage program is under investigation by the U.S. Department of Justice.

The disclosure sent UNH shares tumbling 4.7%, reflecting investor unease with the ongoing troubles with the healthcare stock.

UnitedHealth Group says it is cooperating with federal criminal and civil investigations involving its market-leading Medicare business. The health care giant said Thursday that it had contacted the ...