Update, 5:10 p.m.: Warner Bros. has issued a statement regarding the yanked trailer for “The Hangover: Part II.”

“In our haste to meet the placement schedule for this trailer, we failed to properly vet the final version with the MPAA,” says the statement, e-mailed to me by a studio publicist. “We acted immediately to correct the mistake and removed the trailer from screens.”

It's still unclear which portion of the trailer didn’t meet the MPAA’s vetting standards. (I am guessing maybe that portion at the end involving Zach Galifianakis’s special, um, monkey trick?) If the studio provides more clarity, this post will be updated accordingly.

Original post, published at 3:30 p.m.:

The full-length trailer for “The Hangover: Part II ” — the one that debuted online last week and was posted in many blogs, including this one — has apparently been pulled from theaters. The reason: unclear.

Warner Bros. and the Motion Picture Association of America ratings board issued a notice that asked theater owners to immediately stop showing the preview for “The Hangover” sequel prior to screenings of “Source Code” and in “any other placements.” Theaters also were asked to delete the trailers from their servers. A reader sent an image of the notice to Slashfilm, which first reported the story.

That piece of paper does not explain the reasons for pulling the trailer, and neither the studio nor the MPAA is talking. A representative for Warner Bros. said the studio had no comment and would not even confirm that the trailer had been removed. Howard Gantman, vice president of corporate communications for the MPAA, said all inquiries must be referred to Warner Bros.; he also declined to comment further.

So what gives? Was “The Hangover: Part II” deemed too offensive for general ticket-buying audiences? Is there an objection to Ed Helms’s tattoo? Or is this part of some sort of anti-monkey initiative?

We may never know the answers. But we do know that a third “Hangover: Part II” trailer has been given the go-ahead to roll out in theaters in front of “Scream 4,” starting April 15.