Thousands of school children in Germany suffered from vomiting and diarrhoea over the past few days, which were thought to be triggered by contaminated food in schools.

According to Robert Koch Institute (RKI), a federal health agency, more than 4,000 children have been affected since Tuesday evening.

The cases spread across states of Berlin, Brandenburg, Saxony and Thuringia. Some children have been receiving hospital treatment.

All schools affected had received food from a common supplier, indicating that it was a food-borne illness such as norovirus, said the Institute in a statement late Thursday.

But Sodexo, the food supplier, denied that their relevance with the outbreak.

Health and food authorities of national, state and local levels are investigating the cause of the disease. Many schools remain closed as a precautionary measure.

VietNamNet/Xinhuanet