Police Commissioner Andrew Coster says his staff have turned a number of people around from checkpoints as motorists try to leave Auckland.
He told Newstalk ZB some people had been trying to visit friends and the "odd one" trying to get to their holidays homes.
He says they've turned around 30 to 40 vehicles.
Police closed State Highway 1 at Bombay when they began setting up checkpoints to prevent Aucklanders fleeing the city to dodge lockdown and long queues developed over the day.
Coster says they started the checkpoints when the order came into force that enabled them to do so. That followed criticism from the Thames-Coromandel mayor saying checkpoints should have been in place earlier.
Coster says they've been clear that under level 2 lockdown there's no legal authority for police - or others - to establish checkpoints.
Coster says people are allowed to pass through Auckland in order to return to their normal place of residence.
The police presence at Bombay has also been bolstered by members of the Defence Force assisting with the checkpoint.
Epidemiologist Michael Baker is urging Aucklanders to stay put after last night's announcement that there were four active cases of Covid-19 as a result of community transmission.
Thames-Coromandel Mayor Sandra Goudie said she doesn't blame people for leaving, or wanting to leave, but she hopes that if they were at their bach they stayed in their bubble.
Images of traffic jams have been flooding social media and reports of some Auckland residents travelling hours to get out of the district.
Goudie said it wasn't up to her to tell people what to do, but with Prime Minister Jacinda Ardern announcing level 3 restrictions, people needed to follow her instructions.
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"With the Prime Minister saying stay at home, if you want to keep people safe, you should stay at home. No one knows where it's been in Auckland.
"If people do manage to escape Auckland, because I can't stop it, then I'm just hoping they stick to themselves, they stay in their bubble.
"Stay home, but if you do get here it's a bit late."
She said the Thames-Coromandel district was home to the highest number of over-65s in New Zealand, and an influx of Aucklanders could put them at risk.
"We don't want you bringing it with you, not to the Coromandel where we've got the highest over-65 population in the country.
"If you do escape, stick to your own bubble and be really staunch about that.
"People are getting extremely fearful about the whole situation and for many people with underlying conditions it's a serious risk, so heed the Prime Minister's message."
Baker said he didn't want to see people moving outside of Auckland as that would only make it harder to stop the spread.
"We don't want people to be moving outside of Auckland at the moment because that can spread the virus and there could be a national outbreak.
"The advice would be to stay put at the moment.
"We don't want people suddenly going out of Auckland saying 'I'm just going to go to my holiday home for the next week or two', that's not going to be helpful at all."