Facebook Inc founder Mark Zuckerberg on Thursday said an alleged contract and emails that a New York man says entitle him to a huge stake in the social networking website are forgeries.

In a filing in the U.S. District Court in Buffalo, New York, Facebook and Zuckerberg demanded that the man, Paul Ceglia, immediately turn over the alleged contract as well as the related emails in question.

Ceglia, a wood pellet salesman from Wellsville, New York, has contended that he contracted in 2003 for 50 percent of Zuckerberg's interest in what became Facebook.

Facebook and Zuckerberg hope to use forensic testing to show that the documents that Ceglia said show his ownership stake are fakes.

The contract is a cut-and-paste job, the emails are complete fabrications, and this entire lawsuit is a fraud, Facebook and Zuckerberg said in the filing. When this testing confirms that all of these documents are forgeries, this lawsuit will end immediately.

Christopher Kip Hall, a lawyer representing Ceglia, did not immediately return requests for a comment.

Facebook is privately held, but analysts have said it could be worth $70 billion should it go public, perhaps in 2012. Forbes magazine in March estimated Zuckerberg's net worth at $13.5 billion.

(Reporting by Jonathan Stempel in New York; Editing by Maureen Bavdek)

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