Warren Buffett digs deeper into his big oil bet

Warren Buffett, chairman of Berkshire Hathaway Inc.
Lacy O'Toole | CNBC
Warren Buffett, chairman of Berkshire Hathaway Inc.

After taking a break of nearly two weeks, Warren Buffett has resumed and accelerated his Phillips 66 shopping spree.

In a new filing, Buffett's Berkshire Hathaway reveals that over three days late last week, the company purchased another 2.5 million shares of the energy giant for almost $200 million.

The new purchases were made around $77, $78, and $79 per share. As there can be a lag of several days between purchases and SEC filings, we may find out soon if Berkshire continued to buy.

Over 12 months of buying starting in early January, Berkshire has picked up 10.8 million shares for $832 million, at an average price just under $77.

Berkshire's 72.3 million share stake is now worth $5.7 billion. That's about 13.5 percent of the share outstanding, making Buffett by far the largest shareholder. Number two Vanguard owns 31.8 million shares, about 6 percent of the available shares.

In early trading Monday, Phillips was trading around $79, down 1.5 percent on the day.