boiler water tank ????

Does anybody know how dangerous a what a i think a leaking water tank is. I have 2 water tanks up in the loft, they have been places quite high and not sitting on the floor. The water tanks are in what looks like very hard cardboard. The cardboard has gone all mouldy and looks like there has or there is a leakage and underneath it looks like its about to split open. I had to move back in my house this weekend and refused as I am to scared of something serious happening. Please reply asap