The creators of a popular true-crime podcast have signed a deal worth at least $10 million with E.W. Scripps Co.’s Stitcher podcasting unit, according to people familiar with the agreement, signaling the nascent medium’s rapid growth.

Stitcher is to provide advertising representation and development funds as well as additional resources to support the overall production of Exactly Right Network, maker of the hit podcast “My Favorite Murder.” In the two-year agreement, the companies plan to develop more than a dozen new podcasts.

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