(Bloomberg) -- Occidental Petroleum Corp. began buying back Berkshire Hathaway Inc.’s $10 billion of preferred stock, four years after Warren Buffett’s firm made the investment during the oil producer’s takeover of Anadarko Petroleum Corp.

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Occidental issued “mandatory redemption notifications” for $474 million of preferred stock at a price of 110% of liquidation value plus dividends in March, Berkshire said in its quarterly report. Berkshire still has about $9.5 billion of preferred stock in the Houston-based company, it said.

Separately, Buffett’s firm owns a 24% stake in Occidental common stock and is the company’s largest shareholder, according to data compiled by Bloomberg. Berkshire is willing to buy more Occidental common stock, Buffett said at its shareholder meeting in Omaha this month. However, he ruled out buying the oil producer outright.

Read more: Occidental Drops After Buffett Said Not Seeking Full Control

Occidental had flagged its intent to begin redeeming Berkshire’s preferred stock after record earnings in 2022 helped it repay billions of dollars of debt. The preferred stock carries an 8% annual dividend, making it an expensive part of Occidental’s capital structure.

--With assistance from Max Reyes.

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