The duo previously worked together on "Red Tails," and details of their characters are being kept confidential.
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Paramount, Warner Bros. and a representative for Nolan did not respond to a request for comment, though the three parties haven't confirmed any "Interstellar" casting to TheWrap. Representatives for Oyelowo and Gyasi declined to comment.
The epic sci-fi movie stars Matthew McConaughey, Anne Hathaway, Jessica Chastain, Casey Affleck, Topher Grace, Michael Caine and Mackenzie Foy, as well as John Lithgow, Ellen Burstyn, Bill Irwin and Timothee Chalamet, whose castings were first reported by TheWrap.
Story follows a heroic group of explorers who travel through a wormhole and into another dimension.
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Nolan, who celebrates his 43rd birthday on Tuesday, is producing with Emma Thomas and Lynda Obst. Jordan Goldberg will exec produce with Caltech physicist Kip Thorne, who serves as a technical consultant on the top-secret project.
Oyelowo, who plays Forest Whitaker and Oprah Winfrey's son in "Lee Daniels' The Butler," previously starred opposite McConaughey in Daniels' Southern thriller "The Paperboy." He recently worked with Steven Spielberg and Tom Cruise on "Lincoln" and "Jack Reacher," respectively, and will soon be seen opposite Zoe Saldana in the Nina Simone film "Nina."
Gyasi has worked with Nolan before, having played a prisoner in "The Dark Knight Rises." Gyasi has appeared on "The Walking Dead" and "Doctor Who," and he recently played multiple roles in Wachowski Starship's "Cloud Atlas."
Oyelowo is repped by WME, Inphenate, Hamilton Hodell and attorney Ira Schreck. Gyasi is repped by the Gersh Agency, Anonymous Content and United Agents.