As UnitedHealth Group wrangles with a federal investigation, an executive shuffle and a tanking stock price, a bullish ally has emerged: Warren Buffett. The Eden Prairie-based health giant’s stock price jumped more than 10% before trading opened Friday, following news that Buffet’s Berkshire Hathaway acquired about 5 million shares.

Berkshire Hathaway's $1.6 billion stake in UnitedHealth Group is helping to lift the Dow Jones Industrial Average to a new record as investors pile into healthcare sector funds.