Billionaire Warren Buffett's company bought more than $200 million worth of Occidental Petroleum's shares over the past week, giving it control of 23.6% of the oil producer's stock.

Berkshire Hathaway disclosed its latest purchases of 3.67 million shares in a filing with the Securities and Exchange Commission late Monday. Berkshire has been steadily buying Occidental shares since last February when the price dipped below $60 apiece.

Occidental shares gained more than 3% Tuesday to sell for $61.61 after Berkshire's latest purchases were revealed. Many investors follow Buffett's actions because he is regarded as one of the greatest investors ever.

Berkshire now owns nearly $13 billion worth of Occidental's common shares outright. It also holds $10 billion worth of preferred Occidental shares that pay an $800 million annual dividend and warrants to buy another 83.9 million shares at $59.62 each. Berkshire picked up those warrants and preferred shares in 2019 for helping finance Occidental's acquisition of Anadarko.

Buffett doesn't routinely comment on Berkshire's stock purchases beyond what he is required to disclose, and he didn't immediately respond to questions about this Occidental investment Tuesday morning.

Regulators gave Berkshire approval last summer to buy up to 50% of Occidental’s shares, but Buffett hasn’t offered any indication about how many shares he might be interested in buying. He didn’t address Berkshire’s investment in the Houston-based company in his annual letter to shareholders last month.

In addition to investments, Berkshire owns dozens of companies outright including BNSF railroad, Geico insurance, several major utilities and an eclectic assortment of other companies such as Dairy Queen, NetJets and Precision Castparts.