Facebook Inc. is acquiring the engineering team of Spool, a San Francisco mobile app developer, in another sign of the social networking company's focus on the mobile market. Spool makes apps for Google Inc.'s Android operating system and Apple Inc.'s iOS. Facebook is not acquiring the company or its assets, a company spokesperson said. "The Spool team has deep expertise in mobile software development and a passion for making content easy to consume," the spokesperson said. No financial terms were disclosed. Shares of Facebook were last trading down 4% to $29.48.

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