Key Takeaways Warren Buffett's Berkshire Hathaway increased its holdings in UnitedHealth Group stock.A regulatory filing showed Berkshire held 5 million shares in the second quarter.Berkshire also added positions in D.

Shares of UnitedHealth Group are surging before the market open Friday as Warren Buffett's Berkshire Hathaway disclosed that it recently purchased shares of the beleaguered insurer. Berkshire Hathaway bought around 5 million shares of UnitedHealth last quarter,

UnitedHealth shares rose 6% in extended trading following the disclosure. The stock had fallen nearly 50% this year before the filing. The health insurer, under Justice Department investigation for Medicare billing practices,