But the copies propagated at such a swift rate that the digital cops could not keep up.
BigChampagne estimated the digital film copy had been downloaded in the low hundreds of thousands of times in its first 24 hours on the Internet.
The studio said the F.B.I. and the Motion Picture Association of America were both investigating the film’s premature distribution.
“The source of the initial leak and any subsequent postings will be prosecuted to the fullest extent of the law,” the company said, adding “the courts have handed down significant criminal sentences for such acts in the past.”
Media companies use watermarks and other technological strategies to identify the sources of leaks.
“Wolverine” is not the first film to receive an unintended preview on the Internet. Another superhero film, 2003’s “Hulk,” showed up as a download about two weeks before its release.
But the major studios hoped they had learned enough since then to keep it from happening again.
Mr. Garland said the existence of the illicit file could theoretically depress the box-office receipts for the film, but he emphasized that the online viewers would be only a tiny percentage of the total audience.
The “other fear is bad word of mouth,” he said.
As twisted as it may seem, “you would rather have a very high-quality version of the film leak than a premature working version of the film leak, because it’s not your best work.”
In the case of “Wolverine,” some of the computer-generated scenes were missing and other parts were unedited.
The studio noted that some fan Web sites condemned the leak. But other Internet users downloaded the file and weighed in with reviews.
“This is bad bad news for Fox,” a movie blog called In GOB We Trust said on Wednesday, asserting that negative comments about the film would reduce its box-office prospects.
But the blog reviewed the film anyway, saying that the creators decided to “dumb it down and essentially make a cartoon.”