the last post is highly educational and correct. but on the side, it might seem like an annoyance and it might be just that. However Let me see if I can find pics of what happened to me.
Same thing old house, noise, opened wall for a peak, mold everywhere. mold seems to like damp, cool, dark places, like inside a shower wall. It went everywhere. I ended up tearing all of the walls from the room and others and rebuilding. nip it in the scrotum if you have to.