The World Federation One Stop Fiqh

Ruling 888

If a place in a mosque becomes impure and it cannot be made pure without digging it up or demolishing it, the impure place must be dug up or demolished provided that it is only a little area, or if rectifying the disrespect caused to the mosque is dependent on digging up or demolishing a large area; otherwise, demolishing it is problematic [i.e. based on obligatory precaution, it must not be demolished]. Furthermore, filling the place that is dug up, or rebuilding the place that has been demolished, is not obligatory. However, if something like a brick of the mosque becomes impure, then after it is washed it must be put back in its original position, if possible.