Samples from an Auckland retirement village where two people have died are being analysed to establish whether it has a norovirus outbreak.
A residential hospital wing at St Andrews Village in the suburb of Glendowie has been isolated after 15 people fell ill.
An elderly man and woman, who had pre-existing medical conditions, have died since the weekend and the other patients are recovering.
The centre has 100 in long-term hospital wings and another 80 in other residential care.
Auckland regional public health officials say all possible measures are in place to stop the suspected norovirus from spreading.
The highly infectious form of gastroenteritis causes vomiting and diarrhoea, but health officials say it is not usually a serious condition.
They are advising families of residents to follow the centre management's advice so the outbreak can be brought under control as soon as possible.
The Ministry of Health says an estimated 53,000 cases of norovirus infection occur in New Zealand each year, commonly in hospitals and elderly care homes, although hotels and childcare facilities are also sometimes affected.