A joint investigation by several government agencies is looking into what could have caused 110 students in Nanyang Girls' High boarding school to fall ill last week.

The Straits Times reported on Tuesday that most of the students, who displayed symptoms such as stomach ache and diarrhoea, have recovered and that there have been no new cases.

These symptoms of gastroenteritis were mostly mild and none of the students needed to be sent to hospital. However, the school is still actively monitoring the situation.

Parents were also being kept informed, said the school's principal, Madam Ng Chuen-Yin.

Students said symptoms started to show on Wednesday and Thursday last week.

A joint inspection of the boarding school canteen was carried out on Tuesday by the Ministry of Health, Agri-Food and Veterinary Authority, National Environment Agency and national water agency PUB.

"All the food handlers working at the school canteen have attended and passed the Basic Food Hygiene Course," the agencies said in a statement.

The food handlers were sent for stool screening. Environmental swabs, food samples and water samples were also taken, and testing is ongoing, the statement added.

Meanwhile, the school has been conducting "well-being checks" on students and has disinfected the dining and food preparation areas, as well as the boarding school premises.