The subpoena filed Jan. 18 in the U.S. District Court for the Northern District of California requests that YouTube disclose information sufficient to identify the subscriber so that Fox can stop the infringing immediately.
According to the subpoena from Jane Sunderland, vice president of content protection for Twentieth Century Fox, a unit of New York-based News Corp. (NWS), the four episodes that constituted the season premiere of "24" appeared on the site ahead their TV broadcast, uploaded by a subscriber identified as "ECOtotal."
The subscriber also uploaded 12 episodes of "The Simpsons."
On Jan. 8, Fox said it officially notified YouTube about the infringed episodes and requested immediate removal or to disable access to the service.
News about the subpoena surfaced on the blog Google Watch.
The same group of episodes were uploaded under the username of Jorge Romero on the video site LiveDigital, to which Fox also issued a subpoena.
LiveDigital said the material was taken down right away and LiveDigital intends to comply with the subpoena immediately.
A recent YouTube search revealed only a prequel to Season 6 of "24" and several short clips from The Simpsons.
Calls for comment to San Mateo, Calif.-based YouTube weren't immediately returned.
This isn't the first time Twentieth Century Fox has had a piracy issue involving YouTube. A young user was identified in a case in which a "Family Guy" episode was posted on YouTube ahead of its premiere.
The issue of piracy has sparked concern among entertainment companies and music and video-sharing sites, along with debate about whether the sites should be financially accountable.
FOXNews.com is owned and operated by News Corporation, which also owns and operates the Twentieth-Century Fox film and television production studio.