Thirty-three people showed symptoms of food poisoning after eating boxed lunches made at a supermarket in Seto, Aichi Prefecture, the prefectural government said.
Officials ordered the Shinsen Ichiba Iseya supermarket to suspend operations on Monday after the cases came to light.
Participants at a residents' sports day held Sunday at a Seto elementary school ate the "bento," which included omelets and broiled salmon. None of the victims suffered serious symptoms and all were recovering, prefectural officials said.