OMAHA, Neb. -- Investors soon won't be able to follow Warren Buffett's every move in HP's stock if the billionaire's company keeps selling off shares of the printer and computer maker.

Berkshire Hathaway's ownership of HP Inc. is about to drop below 10% after it sold nearly 5 million shares, according to a regulatory filing by Buffett's company late Monday.

The Securities and Exchange Commission requires investors who own less than 10% of a company to report their company holdings only on a quarterly basis rather than big investors, who must disclose their actions closer to the time of a so-called "triggering" event, which can mean buying or selling shares.

Many investors watch Buffett's moves closely because of his extremely successful track record over the years.

Not that long ago, Berkshire owned more than 12% of HP's stock before it started to trim its stake last month. Now it's down to 10.2% after several stock sales of the Palo Alto, Calif., company.

In the past 30 days, shares of HP Inc. have tumbled nearly 14%, but there has been a fairly broad sell-off across the technology sector. In the same span, shares of Apple Inc. have fallen 9%, but HP is still one of the biggest decliners among peers.

Buffett may be doing more than just trimming the investment, but he doesn't comment on stock sales like this any more than what he's required to disclose because he doesn't want to tip his hand while Berkshire might still be selling. He didn't immediately respond to questions Tuesday on these latest sales.

Berkshire amassed its HP stake early last year. Even after the latest sales, Buffett's Omaha, Neb.-based conglomerate still held more than 100.9 million shares. Altogether, Berkshire has sold just over 20 million shares in the past month.

Throughout his investment career, Buffett has resisted investing in tech companies because he said he couldn't confidently pick out the long-term winners. But in recent years, Berkshire has bought a huge stake in Apple that ranks as the largest investment in its $350 billion portfolio. Buffett has said he considers Apple a consumer products company with extremely loyal customers and that he can understand that kind of business.

Besides investments, Berkshire owns an eclectic mix of companies, including GEICO insurance, BNSF railroad, several major utilities and an assortment of manufacturing and retail businesses including well-known brands like Dairy Queen, See's Candy and Helzberg Diamonds.