UnitedHealth Sinks as Report of Criminal Probe Adds to Woes

UnitedHealth Group Inc. plummeted as much as 18% following a report that the insurer was under criminal investigation for possible Medicare fraud, adding to an already tumultuous week.

The Justice Department has had a probe into the company’s Medicare Advantage business since at least last summer, the Wall Street Journal reported, citing unidentified people familiar with the matter.