The Environment Ministry said it has mislaid a 10-kilogram sample of radioactive soil and other materials sent to it after the 2011 disaster at the Fukushima No. 1 nuclear power plant.
Officials suggested Aug. 14 it might have been mistakenly thrown away due to a lack of communication between ministry officials.
It said the soil does not pose a threat to public health.
Ministry officials said the radioactive soil and other items arrived at the ministry head office in small cardboard boxes in two deliveries from Fukushima city in November 2011.
The radiation level had been recorded at a stable and relatively safe 0.6 microsievert per hour or below, and the soil was preserved in a locked steel case.
The disappearance came to light after the ministry received an inquiry from the media this month asking about the soil.
A subsequent in-house investigation indicated that a ministry employee, unaware of what the case contained, arranged for its disposal in January this year.
A law covering decontamination decrees that “radioactive soil should not be disposed of without a good reason.”
Read more at Ministry loses radioactive soil sent to Tokyo from Fukushima