An inmate has been taken to hospital after a serious assault at a prison on Friday night.
Rumours of sexual offenders receiving "privileges" at Ngawha prison in Northland may have contributed to tensions.
The Herald on Sunday understands a young inmate severely injured a convicted paedophile, aged about 65.
A source said an inmate was smoking, despite a ban in the prison, and that had also contributed to the incident.
Lawyer and prison reformer Peter Williams, QC, said he had heard concerns from inmates at Ngawha at the way sexual offenders were being treated.