Prime Minister Jacinda Ardern says there are consequences for people who break the trans-Tasman bubble rules, even if they don't end up being fined or jailed.

A group of three people from Melbourne have been put into managed isolation in New Zealand after misleading officials about where they were travelling from.

It is understood the trio, who are resident in Australia, planned to attend a funeral during their trip to this country.

They drove to Sydney and then flew to Auckland, and were caught at the border after trying to deceive officials. They will now have to pay for their 14-day MIQ stay.

It appears they broke the trans-Tasman bubble rules - which could lead to a $4000 fine or six months in jail - as well as the Victoria lockdown rules.

Melbourne is subject to a two-week lockdown as the city battles to contain a community Covid-19 cluster.

Restrictions are in place for anyone from Victoria wanting to travel to other parts of Australia.

Ardern said that their mandatory stay in MIQ was a punishment, regardless of whether police decided to charge them.

"Ultimately they were stopped at the border, and they were put into managed isolation.

"That demonstrates that even when we have people who are making a deliberate attempt to get through, that will be picked up.

• Covid-19: Melbourne mourners caught sneaking into NZ; Two acute MIQ cases

"There's multiple points in the system where we can pick people up, and in this case, we have."

Asked why they shouldn't be charged, she said "there are consequences".

"To anyone considering breaching the rules that we have in place - in this case, the family has been picked up, and they've been put into a managed isolation facility.

"As for fines, those decisions do sit elsewhere."

Director-general of health Ashley Bloomfield said relevant border agencies would review processes, even though it appeared this was the result of "disappointing actions" from the three people concerned.

They have all tested negative for Covid-19, and their three-day test results are due tomorrow.

Bloomfield said he hadn't looked into whether the trio should face charges, but added that they may also face charges in Australia for breaking the Melbourne lockdown rules.

It follows a breach of the transtasman bubble rules at the end of April, when a man flew from Perth to Auckland via Sydney while there was a pause on flights to New Zealand from Perth because of an outbreak there.

The man appears to have lied about whether he had travelled from Perth.

By the time his identity and travel were confirmed, he had landed at Auckland airport and eluded authorities. When health officials caught up with him, he was allowed to self-isolate in Northland.

The man's travel highlighted how easy it is to breach the rules in the transtasman bubble, which had only been running for a week at the time of his flight.

Immigration NZ manager Peter Elms said that the time that it was a high-trust model.

The multiple checks included questions being asked at the airport, and data-matching from border agencies to check if people had flown from an area where flights to New Zealand were paused.

But people who drove to an area where flights to New Zealand continued could break the rules by lying about whether they've been in a locked-down area.

"For somebody who's intent on getting to their end destination, regardless of the rules, it's a straightforward option they can take if they're willing to lie," Elms told the Herald in April.

"Quarantine-free travel, certainly when it comes to pauses or suspension, it relies heavily on people's honesty, people's ability to understand and follow the rules in place."