Fresh questions are being raised about prison security after arrests in two prisons on drug-related charges, during a major police operation against an alleged drug syndicate.
Of the 12 people arrested during the police operation on Tuesday, eight were prison inmates.
The union representing prison guards says mobile phone blocking technology is needed urgently in all prisons.
Corrections Association spokesman Bevan Hanlon says mobile phones are difficult to confiscate because they are small and easily hidden.
Corrections Minister Phil Goff says technology to block mobile phone calls will be in every prison by February 2009.
Mr Goff told Morning Report the government has agreements with Vodafone and Telecom to install the devices, which are already in place in Auckland Women's, Manawatu, Otago and Ngawha prisons.
He says New Zealand is way ahead of other Western countries in blocking mobiles in prisons. Mr Goff says all conversations on pay phones in prisons are recorded, and staff are picking up valuable intelligence to pass to police.
Six month investigation
The inmates who were arrested came from Auckland Prison at Paremoremo and the Spring Hill Corrections Facility in Waikato.
The six-month joint operation involved about 180 police, Customs and Department of Corrections staff.
Police say the operation began at 8am on Tuesday with the search of Auckland Prison and Spring Hill Corrections Facility.
Another 20 search warrants were executed at residential addresses throughout Auckland. Detective Inspector Steve Wood says police seized enough chemicals to make 5kg of methaphetamine.
Mr Wood says the chemicals came from China, with parcels coming through the international mail centre at Auckland Airport.
No drugs were recovered from either prison.
Ten men and two women have been arrested on drug-related charges.