TOKYO- Almost 3,500 teachers and students at more than a dozen public schools in Japan's Yashio city have become sick with diarrhoea and stomach pains in a mass food poisoning outbreak.

Saitama prefecture said on Thursday that 3,453 people in 15 elementary and middle schools in Yashio, a city of 92,000 just north of Tokyo, had been affected after eating a lunch supplied by the TQC cooperative on June 26.

Out of a total of nearly 7,000 people examined, more than 2,000 elementary school students and over 1,100 middle school students were shown to have food poisoning, the prefecture said, adding it was investigating the origins of the outbreak.

The lunch included fried chicken, a tuna/potato dish and seaweed salad, as well as rice and miso soup, it said.

Nobody at TQC answered an after hours phone call made by Reuters seeking a comment.

(Reporting by Daniel Leussink; Editing by Alexander Smith) ((daniel.leussink@thomsonreuters.com; Twitter: @danielleussink; +81-3-4563-2747;))