Over 600 students and staff members at multiple schools in Kumatori Town, Osaka have reported symptoms of food poisoning, local media reported on Thursday.
Students and staff members at eight elementary and junior high schools in the town have successively developed symptoms, including diarrhea and vomiting, since a week ago.
As of Tuesday, the total number of those affected reached 633, according to the report.
The local health center detected norovirus in some of the affected students.
The same virus was also found in employees of a company that supplied bread for school lunches to all elementary and junior high schools in the town.
Based on these findings, the public health center determined that the outbreak was caused by food poisoning from bread served in school lunches.
The health center imposed a five-day business suspension on the related manufacturer.