Warren Buffett stuns Wall Street as he snaps up stake in struggling UnitedHealth

Famed investor Warren Buffett has snapped up millions of shares in a company that Wall Street has run away from. 

Berkshire Hathaway has quietly built a stake in insurer UnitedHealth over the past two quarters. 

So far, they've accumulated 5 million shares in the company, a regulatory filing showed on Thursday. 

Buffett, the investor known as the 'Oracle of Omaha,' has a decade-long track record of buying stocks during their dip and riding companies back to profits. 

UnitedHealth is another example. The company has been on a 46 percent slide since January. 

At the beginning of the year, UnitedHealth was trading at over $504. The stock closed today at just over $271. 

The news of Buffett's investment gave the company a quick reprieve: UnitedHealth's share price jumped seven percent in extended trading.  

For years, the insurer was once seen as a dominant stock. Constant profit gains, a reputation for competent management, and all-important insurance contracts gave the stock a halo. 

This isn't the first time Buffett owned the company's stock. From 2006 to 2009, he kept 1.18 million shares of the healthcare company in his portfolio. 

He sold the stake in 2010 amid a broader retreat from the health insurance industry.

This is a breaking news story.