Warner Bros. has a mystery on its hands much bigger than a Muggle.
The first 36 minutes of Warner Bros.' " Harry Potter and the Deathly Hallows: Part 1," which comes out this weekend, appeared Tuesday on the file-sharing network BitTorrent.
A post on the piracy website Pirate Bay indicated that footage came from an internal DVD copy of the movie, commonly called a screener.
But a spokesman for Warner said that no screeners of the new " Harry Potter" movie were created. He said the studio is investigating the leak, and has not yet determined the source.
The leak indicated that despite extensive efforts by Hollywood's film studios to protect their content from piracy throughout production, editing and special effects processes, vulnerabilities still remain.
If the entire movie had appeared online, Warner could have a serious problem on its hands. With only about 25% of "Deathly Hallows" available on the Web, however, it's unlikely that piracy will affect the movie's box office.
Pre-release surveys indicate that it should have a huge opening weekend with receipts in the U.S. and Canada topping $100 million.
Warner Bros.' anti-piracy team will probably have a much bigger problem on its hands soon, as "Deathly Hallows" starts playing in foreign countries such as Australia, Germany and Russia, on Thursday, after which pirated copies are almost certain to start popping up all over the Internet.
Nonetheless, Warner executives are concerned about the early leak.
"This constitutes a serious breach of copyright violation and theft of Warner Bros. property," a spokesman for the Burbank studio said in a statement. "We are working actively to restrict and/or remove copies that may be available," the statement said.
"Also, we are vigorously investigating this matter and will prosecute those involved to the full extent of the law."
Although Web piracy remains a huge problem for the entertainment industry, it's unusual that footage gets out before a movie is released, particularly for high-profile event pictures. The last time a major studio film hit the Internet before its debut in theaters was last year's " X-Men Origins: Wolverine."
An early version of that 20th Century Fox movie was leaked more than a month before it came out in theaters.