They may simply know you desire your passport so badly that they are holding onto it a little longer. That seems to be the case with government and important things anyway. I'm sure there's a reasonable explaination and that it's on its way. If another week goes by, I would definitly call at the info on the link provided to you above. You won't have to worry in any case; UAL Traveler has a good explaination above.

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The world is a book, and those who do not travel, read only a page.
- St. Augustine of Hippo