Cook Islands authorities have reopened schools in Titikaveka closed temporarily by the Ministry of Health last week.
However the reopening is subject to a number of conditions.
These include the establishment of health clinics at two colleges involved n the closure and daily health checks of pupils by Public Health nurses.
Any pupil who shows signs of the mystery illness that led to last week's closure will be checked and sent home if necessary.
The Cook Islands News says the illness does not affect everyone and is not life threatening.
A New Zealand epidemiologist and a toxicologist are expected in the Cooks later this week to help identify the disease.