UnitedHealth Group shares drop 16.5% after inquiry into alleged Medicare fraud

Justice department investigation into health insurance giant reported as company’s CEO says he will retire

Shares in the UnitedHealth Group tumbled after it was reported the largest health insurer in the US is under investigation over possible criminal Medicare fraud.

The US Department of Justice has been investigating the health insurance giant since last summer, the Wall Street Journal reported, citing unnamed people familiar with the matter.