A 6000 cubic metres tank in the paper industry suddenly capsized during a water filling test. Several people witnessed the tilting and fall of the tank. The Council of State nominated an investigation board to investigate the accident as a disaster case. Investigations showed that the foundation slab as well as the foundation piles of the tank were not of the proper dimensions. It was found also that the foundation piles were not driven deeply enough into the ground. New guidelines and measures to prevent similar disasters occurring in the future are outlined.