Apple Inc. has started building its own cellular modem for future devices, a move that would replace components from Qualcomm Inc., Apple's top chip executive told staff on Thursday.

Johny Srouji, Apple's senior vice president of hardware technologies, made the disclosure in a town hall meeting with Apple employees, according to people familiar with the comments. Qualcomm shares dropped 4.4% at 9:37 a.m. in New York.

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