Production on "Sherlock Holmes 2" has been under way in the U.K. since last month. Robert Downey Jr.'s back in the title role, and Jude Law reprises his role as Sherlock's there-in-a-pinch sidekick, Watson. Rachel McAdams, however, hasn't been spotted on set at all.

While rumors have been swirling that McAdams will pop back up, the actress has now been replaced by [article id="1651107"]"Girl With the Dragon Tattoo" star Noomi Rapace[/article] in the sequel's lead female role. Last spring, producer Joel Silver said McAdams will reprise her role, albeit in a less prominent capacity.

So will she in fact join up with Downey and Law, in search of some of the magic that made the original a $523 million worldwide box-office hit last year? Not even McAdams herself is sure, as she explained to [article id="1651807"]MTV News while promoting "Morning Glory,"[/article] a comedy opening Wednesday.

"It's kind of all still in the process," she told us. "They're still doing script work, and we'll see."

The 31-year-old actress said that she's open to reprising her role as Irene Adler, Holmes' love interest and sometime rival, if script issues and scheduling work out. But if she does, it will be for something of a cameo.

"If I do, it won't be a very big thing," she said. "It's not a lead part."

In April, [article id="1638142"]Downey told us[/article] that we very well might not see Irene in the "Sherlock" sequel.

"It's hard to say," he said. "Because Irene Adler only appeared in one of the stories of Doyle's reservoir of activities. But we'll find out quickly."

The Guy Ritchie-directed flick is set to hit theaters December 16, 2011, going up against Brad Bird's "Mission: Impossible IV."

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