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Warren Buffett's Berkshire Hathaway revealed Wednesday it has increased its already large stake in Phillips 66 by six percent to 61.5 million shares.
The additional 3.5 million shares are worth about $282 million at today's closing price of $80.65.
Roughly two-thirds of the shares were bought on Tuesday and last Friday as the stock dipped to around $77 per share.
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Including the newly-purchased shares, Berkshire's stake is now worth $4.98 billion.
In an SEC filing on August 28, Berkshire first revealed that it has been secretly accumulating Phillips 66 shares since the second quarter of this year.