Director-General of Health Dr Ashley Bloomfield says the man who flew from Perth while the travel bubble was suspended with Western Australia could face a fine or time in prison.
Speaking at a 1pm briefing on the vaccine rollout today, Bloomfield mentioned penalties faced by those breaching New Zealand's Air Border Order around quarantine-free travel.
"Penalties could involve a fine of up to $4000 or up to six months in prison," he said.
Bloomfield says investigations into the case of the Perth traveller are still ongoing and there are a number of questions still to be answered, leading to possible penalties.
He wouldn't be drawn into specifics of the case by journalists at this stage.
The man is now in a managed isolation facility after originally travelling to Northland. The breach was found during routine passenger checks after the man arrived in Auckland on Monday.
"It's just unbelievable," Whangārei Mayor Sheryl Mai told RNZ earlier today.
"There's a sense of disbelief and many questions: How did this happen, where is this person? Northland is a large region, are they next door, are they miles away? Did they shop on their way up from Auckland, have they been exposed?
"Just many questions and all of them are unanswered."
The Ministry of Health has classified the man as being "low risk" and quarantine-free travel to and from Western Australia resumed from midday today.