In March 2013, a resident of Takashima, a small town of about 51,000 people on the northwest side of Lake Biwa, discovered something unusual. Along the banks of a local river, someone had dumped, over a more than 500-meter-long area, 77 bags containing 300 tons of wood chips.

Something about the bags aroused local suspicion, but inquiries by local residents to the Takashima Municipal Government the following month produced only vague assurances that the bags were part of a road-paving project along the river bank and that there was nothing to worry about.

As it turned out, there was cause for concern. Local residents continued to pester the city and prefecture for answers, and by August independent monitors had found the bags were contaminated by radiation.