2013 rattle

On the December day my 2013 Prius Five model (hatchback with all the safety add ons, bigger wheels) turned 18 months old, i was on the way to have one of the freebie services. I heard a metallic rattle, seemingly coming from the back of the interior. It continues and I cannot find a source for it. I just read a thread about rattles in the 2011s. Not particularly comforting given what I spent on the car.

Has anyone experienced this? Is this something I could have the dealer chase under the warranty? (this is the first new car i ever bought in my 50 years of driving, so my familiarity with new car warranties is a little thin.)
My dealer has been pretty responsive -- swapping out an interior door panel as a freebie when the armrest portion separated from the lower portion and collapsed into the door.

Thoughts on the rattle appreciated, and thanks.

EliotB
Annandale, Va

 

Thanks for the quick reply. to confess, i have not emptied the tray under the ski slope or emptied the plastic tray under the cargo area that i purchased to hold small items. I will look at that area this weekend. the noise is a very metallic sounding rattle, which is what prompted me to raise the question as it does not sound like plastic on plastic. My first thought was the rear headrest posts when they are in the down/forward position. however, i can still hear something when they are up and locked. The car has a 3/36 warranty, so i guess i still have about 16 months in which to pursue a remedy if I can isolate the noise. Again, thanks for checking in.