3G Capital Partners LP is in advanced talks to buy Kraft Foods Group Inc. through its H.J. Heinz Co. unit, according to people familiar with the matter, in a combination of two iconic brands that would intensify the private-equity firm’s shake-up of the U.S. food industry.

Any deal likely would be valued at more than $40 billion. It could be announced soon, said one of the people, and, according to another, 3G would make it using Heinz. It also is possible the talks could fall apart before a deal is reached.

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