Water in spare tire area

I have discovered water in the spare tire area of my car listed above SI model. Have there been any complaints with this type of issue? What should I do or what should I ask the mechanic to check to repair? The carpet in the trunk is smelly and wet. I have removed the water, tire and have been using carpet cleaner. I have had a fan blowing on the back area for a few days now. Any suggestions on a good carpet cleaner would also be helpful? I will be taking it to the dealer in a few days. Any suggestions on what they might check? Please help.