Eighty-four workers at the Summer Sonic rock music festival here received medical checkups on Sunday after coming down with symptoms of food poisoning, officials said.
Rescue officials received a call at about 9 a.m. on Sunday, saying three workers at the Summer Sonic 2005 venue who had eaten packed lunches were vomiting.
A total of 84 people received medical checkups after complaining of diarrhea and other symptoms, and 42 of them were hospitalized. One of the patients, a girl in her teens, is in serious condition.
Officials at a public health center in Chiba said the patients were restricted to workers at the rock festival. They said it was likely they had suffered food poisoning after eating lunches prepared for workers.
Chiba Prefectural rescue officials said 69 people were taken to a hospital in Chiba after falling ill, and 15 others visited hospitals in the Tokyo Metropolitan area and other districts on their way home.