Moore's Film Company Cries Malpractice Over Sicko Leaks

One source close to the situation said that anti-piracy firms were flooding the Internet with false versions of the film, much as the record industry has with songs.

"We are actively investigating those who illegally uploaded 'Sicko' to the Internet, and we will take the strongest possible legal action," Hurwitz said. The company declined comment about whether it will seek legal action against YouTube for allowing the uploads.

In March, Magnolia Pictures subpoenaed YouTube to obtain the identities of users who uploaded such films as "The Host" and "Jesus Camp." 20th Century Fox did the same thing after users uploaded episodes of "24" and "The Simpsons."

"We cooperate with copyright-holders to identify and promptly remove infringing content," a YouTube spokesperson said. "In this case, the copyright owners used our content-management tools to request removal of the unauthorized clips, and we quickly complied."

The spokesperson said that users still can watch previews of "Sicko" and interviews with Moore on the film's authorized YouTube channel, SickoTheMovie.