How to get rid of mold in shipping containers?

One of my shipping containers is full of mold. I have no clue why that is. Last year it wasn't a problem. My other container doesn't have any mold.
Please give me your ideas on how to fix it.
Thank you!

[@codymclaren3465]

Pre treat with a chemical treatment then pressure wash it. Repeat that a few times as needed. Would think that should do the trick.