Production on Marvel's anticipated ensemble movie "The Avengers" finally kicked into gear last week, but has now shut down following a script leak.

The movie is being directed by Joss Whedon (who previously directed "Serenity" for the big screen) and will tie together threads already put in place in “Iron Man,” “The Incredible Hulk,” “Iron Man 2,” “Thor,” and “Captain America.” The overall plot of the film has been kept quiet but the website Obsessed With Film was recently contacted by an anonymous source offering to sell a copy of the script.

The site, which did not go through with the purchase, received several photographs confirming the authenticity of the script. The photos also confirmed that the script was assigned to Samuel L. Jackson, who will be reprising his role of Nick Fury.

Filming was quickly halted and script revisions have been commissioned for several scenes. It is unclear when production will resume.

"The Avengers" stars Robert Downey Jr., Chris Hemsworth, Chris Evans, Mark Ruffalo, Scarlette Johansson, Jeremy Renner, all of whom will reprise superhero characters from other movies.

"The Avengers" is slated for release on May 4, 2012.