OMAHA, Neb. — Billionaire Warren Buffett’s company has been adding more Amazon shares to its investment cart.

Berkshire Hathaway BRK.B, +0.82% said in filings with the Securities and Exchange Commission on Wednesday that it owned 537,300 Amazon AMZN, +2.49% shares at the end of June, up from 483,300 shares.

Buffett first revealed Berkshire Hathaway’s stake in Amazon in May, although he said one of the company’s two other investment managers made the pick.

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Investors follow what Berkshire buys and sells closely because of Buffett’s successful track record. Berkshire officials don’t generally comment on these quarterly filings.

The quarterly filings don’t make clear who made all the investments. Buffett handles the biggest investments in Berkshire’s portfolio, such as Coca-Cola KO, +0.04% , Apple AAPL, +3.75% and Wells Fargo WFC, +1.37% . He has said that investments of less than $1 billion are likely to be the work of Berkshire’s two other investment managers.

Berkshire’s Amazon shares are worth roughly $950 million.

In the past, Buffett has mostly avoided tech stocks because he said he didn’t understand them well enough to invest in them.

But in recent years, Berkshire has become a major investor in Apple and now Amazon. Buffett has said he values Apple more as a consumer product company than a technology firm.

Besides the Amazon move, Berkshire also increased its Bank of America BAC, +0.64% stake slightly in the last quarter, and it added to its US Bancorp USB, +1.23% stock holdings.