Ice will form in both the fridge and the freezer - the makers arrange to melt it every now and again - hence frost free.
The melt water is channeled to a drain hole at the back where it drips out and evaporates. Sometimes debris gets into the drain hole and blocks it.
If you can't see the drain hole you're not looking well enough - spot the one in the fridge first and then look for the freezer drain.
Good luck...
August 2015