On Monday, the students had a meal of cuttlefish, cabbage soup, sponge cakes, and milk at noon and in the afternoon.

Between 6 p.m. and 9 p.m. that day, around 400 were hospitalized for stomach-ache and vomiting. Many of them were admitted to the District 9 Hospital and other hospitals in the city.

Health authorities also said Tuesday they had banned the circulation of the batch of sponge cakes Thanh Phu had supplied to the school.

Further investigations are continuing to find out other possible causes of poisoning, the inspectors said.

Reported by Thanh Tung