Jersey Shore Cast on Lockdown

Sources connected with the show tell TMZ ... producers want to keep the cast "in the zone" after coming back from Italy. Translation: If they started circulating again in New Jersey with friends, family, and the media, they'd lose the chemistry that makes the show work, and it takes time to get it back.

So given that Season 5 starts shooting on Monday, we're told producers felt it was better to just keep them away from everyone.

But there are always exceptions to the rule. Sammi, Deena, and Pauly D had prior engagements they had booked that could not be canceled -- the girls had commercial shoots and Pauly had a DJ gig in Vegas.