Originally Posted by redline
Is this drywall or plaster?
Being built in the late 40's, it would be plaster. If that were the case, the surface mold would just need to be wiped off with a chlorine/water mixture. It would be odd if moisture permeated the plaster and did no damage to the wall.
An easy way to check would be to scope the walls in a few spots. You can cut a hole the size of a pencil diameter and insert this scope into the wall cavity. It has a light on the end of a fiber optic 36" wand the bends.
I use one to do inspections for problems just like this.