NEW YORK — Warren Buffett’s Berkshire Hathaway Inc. invested $23.9 billion in the third-quarter, the most in at least 15 years, as he accelerated stock purchases and broadened the portfolio beyond consumer and financial-company holdings.

Berkshire bought almost $7 billion of equity securities in the three months ended Sept. 30, compared with $3.62 billion in the second quarter and $834 million in the first, the Omaha, Neb.-based company said Friday in a filing. Stockholdings labeled “commercial, industrial and other” soared 62 percent in the three months to $17.4 billion on a cost basis, surpassing equity investments in financial and consumer-product firms.

“He sees something, and it’s big,” said Thomas Russo, a partner at Berkshire investor Gardner Russo & Gardner.

Buffett, 81, drew down Berkshire’s cash as Europe’s debt crisis and Standard & Poor’s downgrade of the United States pushed stocks to their worst quarterly performance since 2008. The investments disclosed Nov. 4 include $6.9 billion of equities, $5 billion for preferred shares and warrants in Bank of America Corp. and the acquisition of Lubrizol Corp. for about $9 billion.

Buffett is expanding a portfolio that for more than 20 years has included equity stakes in Coca-Cola and Wells Fargo, now the No. 1 U.S. home lender. The chairman and chief executive officer acquired a power company in 2000 and railroad Burlington Northern Santa Fe last year.

“Historically he has preferred consumer products and banking to industrial companies,” said James Armstrong, president of Berkshire shareholder Henry H. Armstrong Associates. “But the market changes, so the names he comes up with changes.”

The S&P 500 Index fell 14 percent in the third quarter, the most since dropping 23 percent in the last three months of 2008. The period’s biggest one-day decline was more than 6 percent on Aug. 8, the first trading day after S&P stripped the U.S. government’s AAA rating. Berkshire spent more on stocks that day than any other this year, Buffett told Charlie Rose in an interview broadcast on PBS on Aug. 15.

Berkshire’s third-quarter net income slid 24 percent to $2.28 billion as the stock market slump pressured the value of Buffett’s equity derivative bets, the firm said in the filing. Insurance units posted a $1.7 billion pretax underwriting gain, while net earnings at the railroad rose 8.5 percent to $766 million. The market value of the stock portfolio advanced to $68.1 billion on Sept. 30 from $67.6 billion at the end of June.

Berkshire’s holdings of banks, insurance and finance stocks advanced 2.7 percent to $16 billion on a cost basis in the three months ended Sept. 30, while consumer products shares fell 5 percent to $12.6 billion. Berkshire’s equity investments include stakes in American Express Co. and Procter & Gamble Co.

Berkshire has disclosed new stakes this year in MasterCard Inc., the world’s second-biggest payments network, and retailer Dollar General Corp. Buffett’s firm has requested permission to omit information from filings that list U.S. equity holdings as of March 31 and June 30. Regulators sometimes let companies withhold data to limit copycat investing while building or cutting a position. Berkshire hasn’t filed its third-quarter stocks statement as of Sunday.