Eleven learners at Sacred Heart Mukumu Girls High School have been admitted to hospital after falling ill on Friday.
Two of the learners are being treated for malaria while nine others were rushed to hospital after complaining of abdominal pain and fatigue.
The students were admitted to St Elizabeth Mukumu Mission Hospital and doctors are closely monitoring their condition.
The principal of the school, Sister Jane Mmbone, confirmed the incident but said there was no cause for alarm as the students were responding well to treatment.
"In fact, three of the students have been discharged after their condition improved and are back in school," said Mmbone.
She said the other pupils reported back to school before they had fully recovered and were being treated and their condition closely monitored.
A nurse has been posted at the school to deal with any emergencies involving students who fall ill before they are referred to nearby hospitals for treatment.
The school was closed indefinitely on April 3 following an outbreak of an illness linked to contamination of water and food.
The school reopened on May 8, with Form Four pupils the first to report, accompanied by their parents.
Students were counseled and those with pre-existing medical conditions were examined by a doctor and their details recorded for medical attention.
Sister Aqminatta Lumili, the diocesan health coordinator for Kakamega Catholic Diocese, said all the students who reported were taken for counselling to help them settle down and resume learning after the outbreak of the disease that had disrupted their studies.
"We are asking parents and learners to tell us if the learners have other conditions that could affect their health, such as diabetes and allergies, so that they can be treated in case of an emergency," said Sister Lumili.
On 15 April, Education Cabinet Secretary Ezekiel Machogu ordered the destruction of the maize to prevent another tragedy.
Last month, a post-mortem examination of the three students and their teacher revealed that they had succumbed to multiple organ failure linked to food poisoning and water contamination.
The school management cancelled all tenders for food suppliers and selected three interim suppliers who have been pre-qualified to supply food to other schools.
The Ministry of Water, through the Lake Victoria North Water Works and Development Agency (LVNWWDA), supplies the school with water from the Tindinyo Water Treatment Plant.
Mr Ibrahim Oluoch, the manager in charge of planning and strategy at LVNWWDA, said water supply from the school's two boreholes had stopped.
"The boreholes need to be flushed and chlorinated before the school can resume pumping water to the nine storage tanks for supply to the hostels," Mr Oluoch said.
An additional borehole being drilled at the school at a cost of 6 million will produce 16 cubic litres per hour. The water will be tested and then pumped to the storage tanks.
The 800 sacks of contaminated grain from Mukumu were destroyed at the Bamburi Cement kiln in Mombasa County.
