Tiny cellphones are being smuggled into a Serco-run prison and inmates are posting gang selfies.
Photos of inmates posing inside and showing off prison ink at the Auckland South Corrections Facility have been circulating on a Facebook page.
The Department of Corrections told 1News extensive searches were carried out after they were made aware of the images, and five cellphones have been found in the prison since January.
Corrections Association president Alan Whitley said the new style of small, finger-sized phones were sought after because they were more easily hidden internally.
The tiny plastic phones are increasingly being recovered as prison contraband. They have been dubbed "beat the boss" devices, where "boss" stands for the "body orifice security scanner".
But mobile phones, including "small phones" had been found during searches, prison director Mike Inglis said.
"Our staff deal with the challenging behaviour of prisoners, many of whom try to disrupt the smooth running of the prison," he said.
"Contraband is a challenge facing all New Zealand prisons and we are constantly vigilant in preventing contraband, including mobile phones. We have robust search, detection and deterrent processes.
"These include searching everyone who enters the prison, technological and personal based detection mechanisms, a full search of prisoners on entry, cellphone detector dogs and regular cell searches."
Inglis said that prisoner who broke prison rules will face internal disciplinary charges, and could also be investigated by police.
Corrections chief custodial officer Neil Beales said the department was made aware of the images in May.
"The phone used was not found and intelligence information concluded that it had been disposed of.
"Technology is rapidly advancing and we are always working to stay ahead of offenders' attempts to manipulate our security processes."
The phones can be bought for $50 online.
Labour Party corrections spokesman Kelvin Davis said prisoners told him phones were smuggled by Corrections' officers.
He said such claims should be treated with caution but he believed some of them were genuine.