Key Points:

An alarm at Auckland's Mt Eden Prison was ignored for nine minutes earlier this year when an inmate used knotted bed sheets to climb to freedom.

A report released today by the Department of Corrections said remand prisoner Aaron Stephen Forden, 26, planned his escape well when he took his knotted bedsheet rope into the roof area undetected and climbed over the wall.

The prison control room was alerted when a prison guard walking to work noticed the knotted bedsheets hanging over the wall and raised the alarm on his cellphone.

Parts of the released report have been blacked out, including one of the factors that lead to the escape and two paragraphs in the conclusion section.

A Department of Corrections spokeswoman said the deletions are in-line with the Official Information Act section which allows information to be withheld "in order to avoid prejudice to measures protecting the health and safety of members of the public". She did not provide any further explanation.

The department said the alarm was turned off after 53 seconds but it was nine minutes before a prison officer used a camera to zoom into the area.

It also said before Forden escaped there was no check on sheet numbers and he was able to accumulate enough sheets to plait together into a rope.

That had now changed and sheets were swapped one for one and cell checks included sheet counts.

The closed circuit television had been upgraded and part of the system damaged by inmates had been repaired and was regularly checked.

The report found the escape was "not a simple escape" and very few people would have had the dexterity Forden showed.

Forden had later told investigators he was acting alone but the investigation team believed that was a lie and his cellmate at least would have known he was making the rope.

The report found it was a concern there was no immediate response to the initial alarm.

"While Forden would probably still have escaped, it is possible the police may have located him sooner had the alarm been investigated earlier," the report said.

Today the department said staffing levels were not a contributing factor and had the prison been fully staffed, Forden would still have escaped.

The report also identified a high level of absences over weekends and this could affect the ability of remand prison staff to carry out checks on prisoners.

However, Beven Hanlon from the prison officers' union said staff shortages were a problem. There was no one to investigate when the alarm first sounded.

"The problem was that the prison was severely short staffed and has been for some time."

He said there were also regular false alarms and when staff looked at the cameras when the alarm sounded they noticed nothing.

The prison officer who was facing disciplinary action over the escape had not been trained on how to use the security cameras.

Mr Hanlon said little had improved and everything that was happening to allow Forden to escape in May, was still happening.