Students at the University of Auckland and two big schools have tested positive for Covid-19.
An email to staff from the University's vice-chancellor, Dawn Freshwater, said the student - a resident at Whitaker Block - attended classes on Monday and Tuesday this week.
The student then travelled to Wellington to be with family before testing positive, Freshwater said.
"The university is working closely with the relevant health agencies on this situation, and is following their protocols, including for contact-tracing, to support our student and to protect the wider university community," Freshwater said.
Residents in the university's Whitaker Block were warned about the positive case.
"We know this may cause concern and be distressing. The university will be in contact with you as soon as we have more information. In the meantime, please try and get a good night's sleep," a letter to residents said.
Meanwhile, students at Auckland's De la Salle College and McAuley High School have tested positive and attended class while infectious.
Letters to parents and caregivers advised them of the news.
McAuley, in Ōtāhuhu, has roll of close to 800 and the student attended class while infectious on August 17.
De la Salle, in Māngere East, has a roll of close to 1000. One of its students also attended the school on August 17 while infectious.
"Aside from visiting a testing facility, you will need to stay at home and self-isolate in
case you become ill with Covid-19. Information about how to self-isolate is available
here. It is important to watch for symptoms of Covid-19 ... while in self-
isolation. Any household members you live with will also need to self-isolate until you return a negative Day 5 test result," the letters to parents said.