Four people are being investigated after more than 120 kindergarten students were hospitalized for food poisoning.

State broadcaster China Central Television, which reported the story on Thursday, said the pupils came from three different private kindergartens in Nanchang, the capital of eastern China’s Jiangxi province.

When the children began to show symptoms on Tuesday evening — including vomiting, headaches, and stomach cramps — they were admitted to Jiangxi Provincial Children’s Hospital for treatment. As of Thursday morning, 32 children were still at the hospital.

He Xin, an employee in the hospital’s emergency ward, told CCTV that while most of the children had stopped vomiting, two remained in serious condition.

Authorities are still trying to figure out what caused the outbreak. According to the CCTV report, the students could have been poisoned by unsafe sponge cake rolls provided by a local bakery that was not licensed to produce food.

China’s Food Safety Law employs a licensing system for food production and trading that requires individuals to obtain a permit before producing food or engaging in catering services. Violation of the law is punishable by confiscation of food-processing materials and facilities.

Yoyo, a teacher at Century Cambridge Bilingual Kindergarten, one of the schools hit by the outbreak, told Sixth Tone that all of the children from her school were back in class by Wednesday. Officials from the China Food and Drug Administration had come to collect food eaten by the children on Tuesday evening, she said.

Nanchang police shut down the bakery and are investigating four people, the CCTV report said.

The director of the Nanchang Food and Drug Administration’s publicity office, a man surnamed Ouyang, told Sixth Tone that the incident occurred hours after his office had announced annual food inspection plans for catering outlets in and around school campuses in the Nanchang area.

The next day, the local food and drug office posted an urgent notice to its website calling for strict implementation of food safety regulations, including rigorous health and licensing checks for catering industry businesses and their staff.

In 2016, a similar incident happened in northwestern China’s Shaanxi province: Forty students from the city of Yulin vomited after eating lunch at their kindergarten, and 35 of them were later hospitalized for treatment. And in 2017, 53 kindergarten students in northeastern China’s Jilin province were diagnosed with bacterial infections after consuming school food.

Editor: Colum Murphy.

(Header image: Children eat lunch at a kindergarten in Mianyang, Sichuan province, April 30, 2009. Zhou Xiaodong/The Beijing News/VCG)