Kevin Polwart still at large

Armourguard has beefed up security following the escape of a prisoner convicted of stealing $600,000 from a security van.

Kevin Polwart, 49, has been on the run since he cut his way through a double perimeter fence at Auckland Prison at Paremoremo on Wednesday.

Armourguard general manager Ian Anderson said the company quickly put additional security measures in place after Polwart's escape.

The "safety and protection" of staff was paramount, he said.

Polwart and his brother were sentenced to 10 years in prison after they were convicted of the armed robbery of an Armourguard van in 1999.

"We reiterate the police warning that members of the public should not approach Kevin Polwart," Mr Anderson said.

His latest escape was similar to a previous break out from Upper Hutt's Rimutaka Prison in 2001, where he used wire cutters.

During his 41 days on the run, he carried out an armed robbery of a security van in Auckland, stealing $600,000 in cash and cheques.

On Wednesday Polwart escaped by using and angle grinder to cut through a steel fence around a concrete yard in which he was working.

He was 14 months away from parole on a 16-year sentence.

Corrections Department national operations manager Robin Benefield said Polwart had been working in the yard for more than eight months.

Security concerns and prisoner employment programmes had to be balanced with the need to prepare inmates for eventual release.

"With any prisoner involved in employment, there is a risk involved. The department has a responsibility to prepare offenders for release," he told the New Zealand Herald.

Inspector Vitale Lafaele, of North Shore Police, said Polwart would be under considerable stress.

He urged him to turn himself in to any police station, from where North Shore police would collect him and manage his safe repatriation.

Police want to hear from anyone who knows where he is.

Polwart is described as a medium build Maori, 165cm tall.