Who made this?

This burrow has appeared underneath one of our pump houses. I'm baffled as to what has made it. e've not seen any rabbits on our place and besides there are usually droppings around the outside of a rabbit burrow, but this is very clean. Bandicoots we have, but they tend to just create little nests amongst grass....some learned friends suggest an echidna...anyway hopefully we shall find the owner sometime soon. Oh and the thong is mine, just for scale....