Police are reviewing more adult sexual assault and child protection investigations, RNZ can reveal.

They are separate to the more than 50 cases of child protection complaints and adult sexual assaults re-opened after concerns were raised in May about Detective Inspector Kevan Verry's handling of a historical case in Northland.

Assistant Commissioner Investigations Corrie Parnell said police understood the re-investigation of those cases would likely raise questions from other victims around the country "as these cases involve serious crimes that have profound impacts on the victims".

"Alongside the re-investigation and systems review phases that are ongoing, Police have an independent team of experienced investigation staff sitting at a national level who will triage any cases that victims or advocates might bring forward to Police."

The team's role would be to "triage and assess" any matters and what further action may be appropriate.

"We are currently reviewing a small number of other cases from around the country not related to the original group of files"

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In relation to the systems review phase, Parnell said police were convening a working group to carry out the work.

"This will be overseen by an experienced Police Leader who has a wealth of experience in this field of investigation.

"The Working Group will review what led to the situation, now named Operation Hark, and ensure that Adult Sexual Assault (ASA) and Child Protection (CP) systems are strengthened. The terms of reference for the systems review is being finalised."

The systems review

RNZ earlier approached police with a series of questions about the investigation including concerns raised about resourcing in Northland and the nature of the cases that are being re-investigated.

It's understood it was a well-known issue that the Child Protection Team and Adult Sexual Assault Team in Northland had a high workload and that staff were being moved off to work on homicides.

In response, Assistant Commissioner District Support Tusha Penny told RNZ Police had assured the public and sector partners that they would be transparent and share the findings when the process was completed.

She confirmed the cases related to allegations of both physical and sexual offending against children and adults.

"Some of these cases relate to historical child sexual offending."

Penny also said police and Oranga Tamariki have established a joint assurance panel to "provide strategic and operational oversight into how these cases are being managed".

"It will also provide reassurance that our systems and protocols for managing these types of investigations, and our support for victims, are robust, and keeping people safe.

"Additionally, Police have established an External Advisory Group to provide expert external oversight and assurance for the current national Adult Sexual Assault and Child Protection reviews underway."

RNZ understands Verry, who has worked in police for nearly 30 years, is on special leave.

He earlier told RNZ: "I can't comment about the matter whilst an employment investigation is being undertaken and police have not provided me with any details of the cases involved."

It is believed the allegations relate to investigations that were closed and did not proceed to court.

It is understood that Verry's role at the time was as a second level supervisor. He would not be involved in investigating the file, but would receive the file with recommendations once the information had been gathered.