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A scene from Harry Potter and the Deathly Hallows: Part 1 with, from left, Robbie Coltrane, Daniel Radcliffe, Bonnie Wright and David Thewlis. A 36-minute chunk of the film has been leaked online just ahead of the film's worldwide release. ((Warner Bros. Pictures) )

Hollywood studio Warner Bros. is fighting off a real-life nemesis as the penultimate film of the Harry Potter   teen wizard series begins screening at theatres around the globe — namely an online file-sharing site that has posted a large chunk of leaked footage.

A 36-minute excerpt of Harry Potter and the Deathly Hallows: Part 1 was "stolen and illegally posted on the internet" earlier this week, Warner Bros. said in a statement.

"This constitutes a serious breach of copyright violation and theft of Warner Bros. property. We are working actively to restrict and/or remove copies that may be available. Also, we are vigorously investigating this matter and will prosecute those involved to the full extent of the law."

The film, the first of a two-part finale based on J.K. Rowling's final Harry Potter novel, opened in some European theatres on Thursday and continues to unspool at cinemas around the globe through Friday.

Industry watchers have predicted a blockbuster opening weekend that could set new records for the hit franchise.

The first six films have earned more than $5.4 billion US at the global box office, according to the box office revenue tracking website Box Office Mojo. The book series has sold more than 400 million copies and been translated into more than 65 languages.

Dan Fellman, Warner Bros. U.S. distribution chief, forecast that the film's box office will surpass $100 million US during the opening weekend in Canada and the U.S. alone.

"This one is heading north of $100 million," he told Reuters, adding that he believes it will also be the first Harry Potter film to make more than $1 billion US worldwide.

The second half of the final tale is slated for release on July 15, 2011.

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Harry Potter stars, from left, Daniel Radcliffe, Emma Watson and Rupert Grint, are seen at the world premiere of Harry Potter and the Deathly Hallows: Part 1 in London on Nov. 11. ((Lefteris Pitarakis/Associated Press))