Quarantine-free travel from New South Wales to New Zealand was paused at midnight last night and will be in place for at least 72 hours.
That followed the announcement of 10 new cases on Tuesday - all of which are believed to be the more infectious Delta variant.
The Premier of New South Wales Gladys Berejiklian said people appear to have picked up the virus while briefly passing through infectious spaces.
The state's Health minister Brad Hazzard said that the Delta variant is the most transmissible strain yet detected.
Announcing the pause to the travel bubble, the Minister for the Covid-19 response Chris Hipkins said the source of the new infections needs to be investigated before travel resumes.
Hipkins added the risk to New Zealand remains low, but there are still several unknowns.
Auckland professor of medicine Des Gorman spoke to Susie Ferguson.