The Herald has learned that six guards were injured in an attack at New Zealand's toughest prison, with three suffering stab wounds to their heads, necks, hands and shoulders after they were set upon by prisoners.

The attack is believed to have been premeditated and kicked off after inmates were handed cleaning equipment, the Herald has learned.

Three guards sustained stab wounds and three others had minor injuries - only one required hospital treatment.

Corrections earlier said only three guards were hurt and have refused to comment further on the attack today.

However a prison source confirmed six guards were involved and hurt.

And, an inmate tried to attack a seventh guard during a major search at the prison today, allegedly throwing a punch but failing to make contact.

In the initial attack, guards were injured when they were set upon by a group of inmates in C Block at Auckland Prison, commonly known as Paremoremo, just before 2pm on Wednesday.

The Herald has learned the attack happened when five of the six inmates unlocked at the time were being handed cleaning equipment by the guards.

In C Block each landing has 12 cells but only half of the inmates are unlocked at a time for safety reasons.

The guards were passing them mops and buckets to clean their cells when the attack kicked off.

The entire prison was locked down as the prison's tactical response team converged on the area to rescue the injured guards and secure the inmates.

One of the guards was taken to hospital and the others to a nearby accident and emergency clinic where they were assessed and treated.

None of the injuries were life threatening.

Corrections have today refused to comment on what injuries the staff sustained, whether weapons were used by the inmates, what sparked the assault and whether charges have been laid against the instigators.

A source close to the prison told the Herald that the attack was planned and had upset the wider prison population.

The source said the guard who was most seriously injured was married with a young family.

"He's very well thought of by the prisoners, no way would he provoke a situation ... He's real nice guy and a gentleman, a pacifist and a lot of the boys are p***ed off he's been attacked," the source told the Herald.

"No doubt he was seen as an easy target ... this was basically a cowardly attack on a gentleman, a kind man.

"A lot of the staff and inmates are distraught by this, especially those who saw all the blood."

The source had been told by inmates in C Block that there was a "blood trail" from the scene of the attack to the medical unit - several hundred metres away.

"There must have been a massive loss of blood by the inmates or staff," the source said.

After the attack the alleged instigators were separated while police examined the scene.

Inmates at Paremoremo believe the attack was planned and carried out by members of the Killer Beez gang.

Corrections refused to comment on that, but confirmed that the gang's notorious leader Josh Masters, jailed for 10 years in 2012 for supplying methamphetamine and conspiring to deal in methamphetamine, was not involved.

Masters is an inmate at Paremoremo but is not housed in C Block.

"The sooner something is done to isolate the Killer Beez gang members from the general prison populace the better as they are nothing but trouble, they don't observe the boundaries that other inmates do," the source said.

Today police and Corrections staff continued a search of C and B Blocks, carrying out "dozens of kleensaks of confiscated items".

While the search took place all inmates in all blocks were locked in their cells.

"They had the whole prison locked in cells for 23 hours until 3pm today while they searched - just an act of collective punishment by intimidation," the source said

"No one outside C Block could possibly have carried out the attack."

Corrections Association spokesman Beven Hanlon said the guards had no warning before they were set upon.

"That morning the staff had done their normal routine, the prisoners hadn't done anything out of the ordinary," he said.

"It was clean-up time so the staff were passing them a bucket and mop - they opened a grille door to hand them a bucket and that's when the prisoners attacked the staff."

Hanlon said he would not be surprised if the attack was gang related due to the high number of patched members in the prison population.

He said guards at all prisons were at risk of being attack every day.

Auckland Prison houses the most dangerous inmates in the country, but that did not mean the risk was any higher than other facilities.

"The risk to staff on a daily basis at that prison is the same as most prisons," Hanlon told the Herald.

"At any time, a prisoner could decide to attack you. It's an inevitable part of what we do, unfortunately."

He said there were procedures and technologies in place to keep them safe.

"At Paremoremo the five that were out and did this attack - that's about as many as you'd get out at any given time, and there were three staff."

A police spokeswoman said the investigation into the assault was ongoing.

Charges were yet to be laid.

She said police could not comment on the specifics of the assault or the investigation.

Increase in assaults on prison staff

According to the Corrections 2014/15 annual report, the number of non-serious and no-injury assaults on staff and prisoners have increased between 2013/14 and 2014/15.

"While this is a matter that requires further strategic focus, it can be seen in the context of improved reporting as a result of the campaign to make violence in prisons unacceptable," the report stated.

"It may also be linked to the increasing number of prisoners on remand (and with indicators of high-risk and complex needs), as these individuals do not have access to the full range of rehabilitative programmes, can be suffering from recent abuse of alcohol or drugs and can be volatile as a result of uncertainty while awaiting trials or sentences."

One of the most high-profile attacks on a prison staffer was the killing of Jason Palmer in 2010.

Palmer, 33, was working at Springhill Prison in Waikato when he was attacked by prisoner Latu Kepu.

Kepu had a record for abusing staff and assaulting prisoners and had threatened Palmer in the past, saying he wanted to "punch him over".

The day he died Palmer went to let Kepu out of his cell for his daily hour of exercise.

He unlocked the cell door and Kepu assaulted the guard, causing him to fall backwards and hit his head on concrete paving, causing fatal injuries.

Kepu was convicted of Palmer's manslaughter.

In 2012 Kepu was investigated by police after allegedly assaulting two prison guards in separate incident on October 20 and 31.

At the time police told the <i>Herald</i> that both guards were taken to hospital and treated for injuries. Neither was seriously hurt and both returned to work soon after.

- NZ Herald