The film’s distributor, 20th Century Fox, said it did not know how the unfinished copy of the comic book adaptation was leaked onto the Internet. The copy was missing many special effects and included temporary sound and music.
Nonetheless, it circulated widely online beginning late Tuesday, even prompting some viewers to publish reviews, favorable and unfavorable, of the hotly anticipated film.
“Wolverine” stars Hugh Jackman in the title role and is set to open on May 1.
The troubling leak — which some people initially dismissed as an April Fool’s Day prank — occurred at a time when media companies are working harder than ever to curtail digital piracy of content.