These white powders are spores, which are like seeds and they will sprout to hypha (fungi fiber). They look like mold, but not. These are a part of mushrooms which are harmless and edible.
In nature, mushrooms sprout in Fall, when the conditions, temperature and humidity, are best for the growth. Hokto mushrooms after packaging are still alive and fresh that they sometimes try to produce another strain of mushrooms. The fungi fibers are part of mushrooms and are safe to consume.