The 'Toxic' singer has been in Las Vegas since Tuesday (30.01.07) working with Lukasz Gottwald, who has previously collaborated with Missy Elliot, Mos Def and Kelis.
A source told People magazine: "Britney is really pulling out the big guns on this album. She's been partying a lot lately but she's been working in studios in Miami and Los Angeles too.
"She's rehearsing material, working hard and having fun all at the same time."
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