A regulatory disclosure showed Berkshire Hathaway (BRK.A,BRK.B) raising its stake in the oil and gas giant in Occidental Petroleum ( NYSE:OXY ). Following the news OXY stock was up almost 3% in pre-market trading Friday, reaching $46.70. With purchase prices ranging between $45.80 and $46.56, Berkshire Hathaway bought an extra 8.9 million Occidental shares in multiple transactions, according to a Securities and Exchange Commissionreport. The transaction raises Berkshire Hathaway's already sizeable Occidental ownership.

By lowering well and drilling expenses, Occidental has concentrated on increasing operational efficiency, therefore allowing the company to raise its operating margins from 53.72% to 57.01%. The energy business has also worked on improving its balance sheet metrics, to enable continuous dividend and share buyback returns for its shareholders. The growing share of Berkshire Hathaway points to ongoing faith in Occidental's long-term performance and its importance to its portfolio, following a sequence of investments made by the company in Occidental starting in 2022.

This article first appeared on GuruFocus .