NEW YORK — S&P Dow Jones Indices says it will soon add two well-known U.S. companies to the S&P 100.

Automaker General Motors Co. will replace H. J. Heinz Co. in the S&P 100 and 500 indices on Thursday. The ketchup maker's acquisition by 3G Capital and Warren Buffett's Berkshire Hathaway is expected to be complete by then.

Insurer American International Group Inc., known as AIG, will replace oil service company Baker Hughes Inc. on the S&P 100. S&P said Monday that Baker Hughes' market capitalization has dropped below $21 billion and is no longer appropriate for the index. Baker Hughes will remain in the S&P 500.

GM shares rose $1.17, or 3.4 percent, to $35.59 in after-hours trading.