The new cells. Pic: NZPA

Wellington, June 25 NZPA - Two shipping containers have been turned into prison cells and a shower block at Rimutaka Prison in the Hutt Valley, but they won't be housing inmates any time soon.

On Tuesday, Corrections Minister Judith Collins said double-bunking and container cells would be needed to avoid a prison bed crisis due to peak early next year.

But Corrections Department chief executive Barry Matthews told reporters today at Rimutaka Prison that the department was "concentrating on double-bunking first" and the containers would not be ready until next year after security issues, resource consent and building code requirements had been met.

"These ones have quite a bit of fit-out to be done for security purposes," said Derek Lyons, Corrections assistant general manager for systems and infrastructure.

"They have pretty standard domestic fittings so far with some security components."

Corrections believes it will be able eventually to put the container cells on prison sites at a cost of $53,000 to $63,000 per bed -- or about half the cost of conventional cells.

Apart from the cost-saving, Mr Lyons said the other advantage would be trucking the fitted-out container units into prisons, ready to use, reducing the security risk of having contractors and their work tools in prisons for extended periods.

Shipping containers had been used in West Australian prisons for about 15 years, as well as in Australia's Northern Territory, Norway, Britain and the United States, he said.

Corrections had worked off Australian plans but was factoring in New Zealand cell standard requirements, Mr Lyons said.

The container cell unit at Rimutaka is fitted out with four insulated and heated cells measuring six square metres each, so the cells are slightly larger than the 5.7sq m single-bunk cells at one of Rimutaka's minimum security units.

But Mr Lyons said if the containers were to be double-bunked, they would be configured as three cells per unit which would keep them within the United Nations requirement of 8sq m per cell.

Mr Matthews said Waikeria Prison in the Waikato was one of the sites being considered for using the container cells.

New Zealand's burgeoning prison population is forecast to require 5000 extra beds by 2018.