Julius Green, a Christie expert who has produced more than 250 plays and musicals, found five full-length plays and five one-act dramas written by the creator of the fictional Belgian detective, Hercule Poirot, while scouring archives containing her papers.
Some are previously unknown and the others long forgotten. Most of the plays are murder mysteries.
The material lay in several archives, including those of Christie's family and her theatrical producers, to which Green was given unprecedented access.
They include adaptations of Towards Zero, her 1944 novel, and The Stranger, a thriller about a woman who discovers her husband is a serial killer.
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Others are The Clutching Hand, showing the investigation of a series of murders by Craig Kennedy, a detective created by the American writer Arthur B Reeve, and Someone at the Window, inspired by a short story of Christie's called The Dead Harlequin, 'The Sunday Times' reported.
There is also a three-act domestic drama called 'The Lie' which is about infidelity and was written during the failure of Christie's marriage to her adulterous first husband, Archie Christie.
Green found the script for Towards Zero in the archives of the Shubert Organisation, the oldest theatrical production company in America. The 1945 work is "entirely different" from Gerald Verner's stage adaptation 11 years later.
Green said there was "huge potential" to bring some of the "new" plays to audiences.