Police are hunting for a "dangerous" prisoner who has escaped from Waikeria Prison in Waikato.
William Kaitipa, 43, escaped from a medium-security unit at the prison, near Te Awamutu, about 3am on Tuesday.
The Department of Corrections says it is believed Kaitipa scaled a five-metre security fence after levering open and breaking a fanlight window in his cell.
Another inmate was also trying to climb the fence but was caught by prison staff.
The department says Kaitipa was jailed in 2000 for sexual attacks and burglary. He is serving a sentence of preventive detention and is not eligible for parole until 2013.
Police say Kaitipa has a long history of violent offending, with more than 20 convictions, and should not be approached.
He is described as Maori, with copper-coloured wavy hair. He has a tattoo of a bird on his neck and a glove on his forearm.
Police believe Kaitipa may flee to Bay of Plenty or Pukekohe, near Auckland, as he has gang links to those areas.
On Tuesday, the department defended keeping Kaitipa in a medium-security unit despite him being on preventive detention.
Corrections regional manager Dianne Brophy told Checkpoint Kaitipa had been in a high security part of the prison, but had earned the right to be moved to a medium-security area about a year ago.
However, Ms Brophy says Kaitipa will be reclassified as a high-security prisoner when recaptured.