A puzzling new outbreak of the coronavirus in New Zealand’s largest city has grown to to 17 cases, with officials saying the number will likely increase further.

And a lockdown in Auckland designed to extinguish the outbreak could be extended well beyond an initial three days, according to an AP report.

The source of the new infections continues to stump officials. Director-General of Health Ashley Bloomfield said genome testing has not yet matched the new cluster with any infections that have been caught at the border, although the testing has indicated the strain of the virus may have come from Australia or Britain.