About 30 students of the government school at Pandurangapuram in Khammam urban mandal fell ill after eating mid-day meal on Wednesday.
The students were rushed to Khammam hospital.
Horticulture minister Ramreddy Venkata Reddy was gheraoed by student union activists when he visited the hospital to enquire about the health of children.
Demanding action against those who were responsible for the incident, CPM activists staged a dharna in front of the hospital.
All the 30 students are stated to be out of danger.
Venkata Reddy said a special committee would be set up to probe the incident.
District collector Siddharth Jain visited the hospital and promised to initiate action against the educational officials for negligence.