Unusually potent urine

[Sinfonian]

One of my chinchillas has what I would describe as an abnormally potent urine smell coming from her cage/bedding. I change all of the cage bedding regularly, and neither of the other two chins/cages has a smell even close to this one. I thought it might be the litter pan itself, so I scrubbed it out really well and filled it with fresh bedding. A day later, it reeks again. She and her cage didn't have this kind of smell when I first brought her in, so I'm a bit stumped. This is the chin I suspect may be pregnant--could that have anything to do with the smell? Are there any other possible causes?