UnitedHealth falls after WSJ report on DOJ investigating co's Medicare billing

** Shares of health insurer UnitedHealth Group UNH fall 2% to $301.82

** Investigators from the U.S. Department of Justice are questioning former employees of UNH over how the company deployed doctors and nurses to gather diagnoses that bolstered its Medicare payments, the Wall Street Journal reports, citing people familiar with the matter

** Former employees are being questioned as part of an ongoing criminal probe into UnitedHealth Group for potential Medicare fraud, which the Wall Street Journal first reported in May

** Employees had been questioned by prosecutors working for the healthcare-fraud unit in recent weeks, the report says

** The Federal Bureau of Investigation and the Department of Health and Human Services' Office of Inspector General also participated in some of the interviews, according to the report

** UnitedHealth says in a statement it stands "firmly behind" the integrity of it Medicare Advantage business

** It also said the WSJ article was "relying on incomplete data, a predetermined narrative and a flawed understanding of how the Medicare Advantage program works"

** Including session moves, stock down 40.2% YTD