Nelson-Marlborough District Health Board's Chief Medical Officer says it's too early to say how large the latest Covid-19 outbreak in the region will end up.
The number of new cases has jumped by nine, to 14 active ones.
The cases are made up of two clusters.
Dr Nick Baker said finding the link is important and it may take some time.
"We don't know with the cases we've seen in the two small clusters whether we're close to the point at which Covid entered our community or whether we're distant and that will go a long way to determine the number of cases that we get over the coming days and weeks."
Dr Baker said the region's high rate of vaccination will protect many people from a severe form of the virus.
He said the cases are made up of two clusters, with 11 in one and three in the other.
"Covid is here, we can expect case numbers to increase and this is something that we've been planning for, it's now time to activate all of our plans and fine tune them. It's also very important that the community knows to double down and take all the precautions that will make life hard for Covid."
Dr Baker said a possible connection between the two clusters is being investigated.
Two schools in Nelson - Enner Glynn School and Broadgreen Intermediate - have had cases. Both schools have temporarily closed while contacts are located.