Two inmates at Hawke's Bay Regional Prison are in isolation amidst fears they may have contracted the coronavirus - but one is refusing to be tested.
Corrections National Commissioner Rachel Leota said the two inmates both arrived only recently at the prison.
"One has been tested as a precaution and we are awaiting the outcome of the result. One is declining to be tested and remains in isolation. Staff are committed to supporting his health and wellbeing and are doing everything possible to encourage him to undertake testing."
Five prisoners at Mt Eden prison in central Auckland had also been tested for Covid-19.
"Test results have been returned for all five prisoners - they are negative, they do not have Covid-19. No cases have been confirmed at any of our sites," Leota said.
To prevent the virus spreading in prisons, all new inmates were being isolated for two weeks on arrival.
Corrections said it had already stopped private visits to prisons and all releases to work activities on 24 March.
After the level-four lockdown Corrections brought in new measures including suspending face to face visits by legal advisors although inmates could still get legal advice over the phone.
Prisoners are being given a $5 phone card each week until visits resume. Email is also being made more easily available to inmates.
Corrections said prison guards are now wearing disposable gloves and masks and that gowns and eye protection was also used if a prisoner was suspected of having Covid-19.
There are about 10,000 people in jails across the country and justice reform advocates have been calling for the prison population to be reduced amidst fears the virus could spread quickly in jails.
About 6 percent of the country's inmates are over 60 years old. Older people are more vulnerable to Covid-19, and the Ministry of Health has advised over-70s to be particularly stringent with self-isolating.
But the majority of the country's inmates are between 25 and 49 years old.