A collegiate spokesman said extra cleaning has taken place to ensure a minimal amount of cross contamination.
"Extra hand sanitisers were placed throughout campus and a reminder of the importance of practising good hygiene through hand washing was given."
Headmaster Chris Moller sent out a precaution email notifying parents of the gastro outbreak.
Isolation areas have been set up in the boarding houses to minimise transmission and staff are continuing to observe over the next 24 hours.
Mr O'Connor has advised the school of a number of measures including isolation of cases, hand-washing, laundry, cleaning, and provision of food.
"The numbers of new cases have decreased each day, and we are aware of three new cases today," Mr O'Connor said.
The school said they were happy to report that the well-being of the majority of the students has returned to normal and only six students were still in an incubation period, on the advice of the WDHB Public Health Services.