Investigations showed that excavated dirt piled next to the building may have caused the collapse.

An attempt had been made to dig a tank in the garden, but the subsoil water proving too low, it had been abandoned, unfinished, with the excavated earth left piled up into a hillock.

Cano, a 63-year-old microbiologist at California Polytechnic State University, San Luis Obispo, inspects the smelly little mounds lovingly.

Schools all over Fukushima, for now, either have buried contaminated soil or piled it in one corner of their properties. It isn't clear how long the soil will stay there.

On the top of each was a hole, the edges of which were defined with twisted logs, set flush into the ground, like wooden lips.