The Department of Health is investigating a suspected food poisoning outbreak affecting more than 50 students from a Tseung Kwan O primary school.

Aged seven to 15, the students ate food including sushi provided by a supplier during lunchtime. The majority developed nausea and vomiting within one to two hours. Their symptoms were generally mild.

As at 6pm, 58 were seen at United Christian and Tseung Kwan O Hospitals. So far, none have been admitted.

Investigations suggest it was an outbreak of bacterial food poisoning. Food & Environmental Hygiene Department officers are investigating the food factory supplying the sushi.

With the approach of summer, the department called on people to be wary of food-borne infections as bacteria multiply faster in higher temperatures.

To prevent food-borne illness, people should:

* clean and cook food thoroughly before consumption, particularly shrimp, crab, oysters and clams;

* wash hands before eating and after going to toilet;

* handle raw and cooked food with separate utensils to prevent cross contamination;

* keep raw and cooked food separately;

* store food in refrigerator (at four degrees Celsius or below) and adequately reheat leftover food before consumption; and,

* keep the environment clean.