Warren Buffett's Berkshire Hathaway bought 5.9 million more shares of Occidental Petroleum (OXY) May 2 and May 3, Bloomberg reports, citing a Securities and Exchange Commission filing on Wednesday.

At the Berkshire Hathaway annual meeting last weekend, the company announced it had a 14% stake in Occidental. Buffett said after reading Occidental's annual report, he decided the company was a "good place" to invest, Fox Business reports.

Berkshire Hathaway now has a 15.2% interest in Occidental Petroleum, which was the best-performing stock in the S&P in the first quarter of 2022, returning 81.8%. By some estimates, however, OXY was up more than 100% in the quarter.

This week's investments for Berkshire come in addition to the preferred stake it acquired in 2019, when Occidental bought Anadarko Petroleum.

Over the weekend, Berkshire also secured more Chevron (CVX) shares.