A West Auckland high school has been forced to shut for deep cleaning after a student tested positive for Covid-19.

The Ministry of Education informed St Dominic's Catholic College of the news on Tuesday afternoon, parents were told.

Principal Anna Swann said the college for girls would be closed for 72 hours to be deep cleaned and would reopen next Monday.

"I understand that this may cause some feelings of worry and concern among some families, but I want to reassure you that we are being closely guided by the Ministry of Education and the Ministry of Health," Swann wrote in a letter to parents.

"If you know the identity of the student of family with Covid-19, please do not disclose their names or details to anyone else, and discourage your children from speculating or identifying them on social media."

Such speculation could lead to online bullying and abuse, she said.

All school activities due to take place at the secondary school, including senior preliminary exams, were on hold until further notice, Swann said.

Only cleaning contractors would be allowed on the school grounds over the next 72 hours.

Henderson North primary school is a mere nine minute walk from the school.

Holy Cross Catholic School principal Janice Borsos shared the news about St Dominic's Catholic College with parents this evening.

"I am requesting that you keep any children home who have a sibling at the College," she shared online.

"Yes I am being very cautious but I am trying to keep all our children safe."

Meanwhile the Ministry of Health announced six new cases of Covid-19 today, four in the community and linked to the Mt Roskill Evangelical Fellowship Church "mini-cluster".

Auckland Regional Public Health was actively tracing and testing their contacts.

Two of the cases are in managed isolation - one is a man in his 20s who arrived from the Philippines on September 3 and was at a managed isolation facility when he tested positive on day 3 of his stay.

The second case is a female in her late teens who arrived on the same flight from the Philippines and also tested positive on day 3.

Four people with Covid-19 remain in hospital: two are stable and in isolation - one in Middlemore and one in North Shore hospitals - and two are in ICU, at North Shore and Waikato hospitals.

With today's six new cases and one additional recovered case, New Zealand's total number of active cases is 123. Of those, 43 are imported cases in managed isolation facilities, and 80 are community cases.