The Corrections Department says an inmate at Auckland Prison at Paremoremo used a tool from the prison workshop to escape.
Prison authorities noticed just before midday that Kevin James Polwart, 49, who was serving a sentence for armed robbery, had cut through two wire perimeter fences.
It's not the first time he has escaped; it was reported in June 2001 that he broke out of Rimutaka Prison using the same means.
Corrections says Wednesday's escape was notified just before midday.
Area Commander Inspector Les Paterson says the time between when Polwart was last seen and when the police were alerted would have given him a good head start.
Inspector Paterson says the local area is mostly bush and lifestyle blocks making the search slow and difficult.
He's urging residents who are returning home from work this evening to check their homes for any signs of forced entry before going in.
He says Polwart, who he believes was in a lower security unit when he broke out, should not be approached.
Traffic delays are likely as police search the area.
Members of the public are advised not to approach anyone acting suspiciously or give anyone a lift in their vehicle. Nearby residents should also check their houses and vehicles are secure.
A resident living close to the prison is angry at the length of time it took for her to be notified of the escape. She says despite being on a list at the prison, it was two hours before she was rung.