Is this mold in the walls or something else?
In the San Fernando valley 30 miles north of Los 
Angeles a family member died. Leaving the spouse 
alone. Mysteriously 7 years later the remaining 
spouse died. When the coroner came, he thought 
their was a death their in the past. Records confirmed 
what he thought. There was a lot of mold between
the studs, and behind the walls. 
My point is, if you don't know find out quickly. It can be concluded with a test of the air over a period of hours?!
Don't wait. Come to a conclusion professionally.
Painted for 7 years. Dealt with minor stuff, maybe 
10 square inches in the past. Did train with a 
firm that taught me what to look for when bidding
for new work. 
I would contact my insurance company and go
from there. Get informed quickly.