Toby Jones, who appeared in Walden's first quarter release Amazing Grace, has been cast as the Mayor's right-hand man, while newcomer Saoirse Ronan will play one of the teenagers, Lina Mayfleet.
Gil Kenan will begin shooting this summer in Belfast and Twentieth Century Fox will release in North America on Oct 10 under the Fox Walden joint venture.
Summit International is handling overseas sales and was selling rights in Cannes last month.
City Of Ember centres on two teenagers who must save their town from encroaching darkness. Playtone's Gary Goetzman and Tom Hanks will produce and John D Schofield will serve as executive producers.
Walden Media head of production Alex Schwartz and creative executive Bonnie Solomon will oversee the project for the company.
Murray's deal was negotiated by attorney David Nochimson of Ziffren, Brittenham, Branca, Fischer, Gilbert-Lurie, Stiffelman, Cook, Johnson, Lande & Wolf, with Walden Media chief operating officer Jess Wittenberg and executive vice president of business and legal affairs Jim Meenaghan.
Jones is represented by UTA and Ronan is represented by CAA.