OMAHA, Neb. (AP) — Berkshire Hathaway revealed four new investments last week in steelmaker Nucor, insurer UnitedHealth and two of the nation’s biggest homebuilders — Lennar and DR Horton — but it’s not clear if the investments are big enough to ensure that legendary investor Warren Buffett handled them.

Buffett, who plans to retire as CEO at the end of the year after six decades of building Berkshire, handles all of the conglomerate’s biggest investments worth $1 billion or more. Three of the new investments disclosed in a filing with the Securities and Exchange Commission are worth less than that, so they could be the ideas of one of Berkshire’s two other investment managers.

Yet Berkshire’s new UnitedHealth stake was worth $1.57 billion, so that one could be big enough to be Buffett’s handiwork. Berkshire got permission from the SEC to keep the other three investments confidential earlier this year while it built those stakes, but it apparently bought nearly 5 million UnitedHealth shares just in the second quarter.

Berkshire’s filings simply offer a snapshot of its $258 billion portfolio at the end of the second quarter. Many investors comb through Berkshire’s filings every quarter because they like to follow Buffett’s moves. His record of trouncing the S&P 500 for decades has inspired legions of followers.

The filing doesn’t make clear who at Berkshire handled each investment. Besides Buffett, Ted Weschler and Todd Combs also pick stocks, but they generally handle smaller portfolios and Combs also serves as Geico’s CEO. Yet Buffett has had a hard time finding stocks or any other investments in recent years that he wants to invest much of Berkshire’s $344 billion cash in.

Berkshire’s Nucor stake of 6.6 million shares was the biggest new investment worth roughly $857 million at the end of the quarter. The Lennar investment was worth nearly $800 million, while the DR Horton stake was much smaller, worth $191.5 million.

Buffett already knows quite a lot about the home building business because Berkshire owns the nation’s largest manufactured homebuilder, Clayton Homes.

Besides stocks, Berkshire owns dozens of companies in a variety of industries including Geico insurance, BNSF railroad, several major utilities and an assortment of manufacturing and retail companies. The Omaha, Neb.-based company’s holdings include many well-known brands such as See’s Candy and Dairy Queen.