20th Century Fox has issued YouTube with a subpoena after episodes of The Simpsons and 24 appeared on the popular video site.
The subpoena was filed on 18 January in the US District Court for the Northern District of California.
YouTube has been asked to provide the identity of the user who posted 12 episodes of The Simpsons and the first episode of the new season of 24.
The pirated episode of 24 appeared before the programme was even shown on television.
The identity of the person who posted the clips is known only as 'ECOtotal' but it is likely that they either work in the studio, or are a member of the press who received preview copies of the shows.
Video site LiveDigital was also found to be hosting the same material, posted by a user called 'Jorge Romero', and has been included in the subpoena.
The offending material has now been removed from both sites.
20th Century Fox has already sued YouTube for the names of its users after the video site hosted pre-release footage of Family Guy.
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