Warren Buffett's Berkshire Hathaway on Saturday reported a lower operating profit in the first quarter, hurt by weaker results from its insurance operations, while its cash pile continued to grow. Operating profit for the Omaha,

Investors often use Berkshire Hathaway's quarterly-filed Form 13Fs to track Warren Buffett's trading activity. Buffett has been a net seller of stocks for nine consecutive quarters, which has ballooned Berkshire's cash pile to $334 billion.

Berkshire Hathaway (BRK-A, BRK-B) shareholder meeting is underway. Called "Woodstock for Capitalists," the weekend's main event kicked off with legendary investor Warren Buffett taking questions from CNBC's Becky Quick and Berkshire shareholders.