About 1,100 bottles containing liquid radioactive material have been found unattended on the campus of the University of Tokushima, the education ministry said Monday, warning the university to improve its control of hazardous materials.
The Education, Culture, Sports, Science and Technology Ministry issued a written reprimand to university President Toshihiro Aono.
Radioactivity levels on the surfaces of the bottles were low, and there are no signs of contamination in the surrounding areas, the ministry said, adding that there is no danger to humans and the environment.
The unattended bottles, most of them 20 milliliters in capacity, were found on shelves in laboratories, refrigerators along corridors and other research facilities.
Most contained tritium, while some had radioactive materials from reagent chemicals.
The ministry learned through inquiries of personnel at the university that some of the radioactive materials had been taken by professors out of controlled areas without permission and were used for experiments at laboratories between 1976 and 1997, ministry officials said.
According to the university, the professors have explained that they took the materials because it was more convenient than bringing test tools into the controlled areas.
University officials said they plan to punish the professors.
They said the ministry also found that an isotope center managed by the university has been keeping banned types of radioactive substances, including strontium.
The ministry ordered the university to conduct an internal probe following the discoveries of radioactive substances in its laboratories in June and July.