Oranga Tamariki has removed two staff members from residences after "serious allegations" of "inappropriate sexual behaviour".
Chief executive Chappie Te Kani has, over the past week, been informed of two allegations involving staff acting inappropriately towards young people in Oranga Tamariki residences.
He said it was "unacceptable", with "no place for it in our organisation or in our communities".
"My priority is the safety and wellbeing of the young people involved in these allegations."
He said police were brought in "immediately" after he was notified and were investigating the claims. Oranga Tamariki was also conducting its own investigation. About five young people were affected. All the alleged incidents took place within the last year.
"I know that there will be rightfully further questions about the specific allegations, but can I please ask that we allow the investigations to take their course. I give my assurance that the outcomes of these, at the appropriate time, will be made public.
"However, I made the decision that I was not prepared to wait for the outcome of any investigation. Whilst these are currently individual and isolated incidents, one is one too many."
The two staff were not connected in any way, he said, with concerns brought up separately by other staff members.
"Both staff are not in the residences, they are not working with young people."
They were working in residences, across both youth justice and care and protection residences, in different facilities to one another.
Former Police Commissioner Mike Bush will take on leadership of all Youth Justice and Care and Protection residences, and "lead a rapid review across all our residences, including our Oranga Tamaraiki community-based homes", Te Kani said.
Bush will be assisted by Whaea Shannon Pakura, a former chief social worker and member of the Government Ministerial Advisory Board to the Minister for Children.
It was expected the review would take two months, after which the findings would be made public.
"For them, what we're doing is the police investigation, alongside Oranga Tamariki, with our child protection protocol, we'll continue to do those investigations," Te Kani said at a media conference on Wednesday morning.
The young people affected have all been contacted and Oranga Tamariki was working with all whānau. Social workers would continue to work alongside them.
"But right now, what we can say is all of the young people have all the support they need around them."
Te Kani said he would "absolutely" be meeting with the whānau himself.
"It's an absolute breach of trust, I mean, I am incredibly upset about this happening inside Oranga Tamariki, I'm very upset... it really damages the awesome mahi that many of our kaimahi do every day, they are absolutely let down by the actions of two individuals."
Asked whether the residencies were safe after the two staff members had been removed, Te Kani said Oranga Tamariki had "done a lot of work since finding out these allegations, understanding what problems we may well have and we need to do the work to get the assurance that all of our young people across our residences are safe".
Te Kani was asked again if he was confident young people were safe. He responded: "I am confident that those allegations against the two people are no longer at the residences, we have removed that risk".
Asked if he was confident there was not a culture issue at the residences, he said: "I am confident that we are doing our very best every day, but Mr Bush is here to give us that assurance across our residences".
An in-depth independent review would take place right across the residences, Bush said.
"It's important that we understand if there are any other issues, because our priority on behalf of the chief executive is to ensure all of the tamariki, all of the young people in the residences, kaimahi, all of the staff are safe and that the community are also safe."
Bush said they would talk to the tamariki, staff, stakeholders, iwi and all oversight groups involved.
Te Kani said he had every confidence in the leadership team, but it was important to bring in Bush's experience and independent view.
Minister: 'When there's a second incident - is there a pattern?'
Children's Minister Kelvin Davis, who has responsibility for Oranga Tamariki, said what happened had been unacceptable but praised the chief executive for acting "swiftly and decisively".
"Most important thing for me is making sure that the children or young people are safe in these residences. Obviously that did not occur in these instances but I think that the appointment of Mike Bush is the right move to make in order to get to the bottom of it."
He said he found out about the first instance nearly two weeks ago on 8 June, but the news of the second had been cause for stronger action.
"If there's one incident you think 'Okay, deal with it', but when there's a second incident - is there a pattern? That's why it was really important that this investigation, this review by Mike Bush, is set up.
"My understanding is that both issues were raised by staff and I just want to acknowledge the staff who did do that - they did the right thing. I think it's good that staff are realising that they have to put the safety of the children and the young people as their first priority.
"I do encourage all staff if they see something inappropriate happening to raise it and not just leave it once they've raised it ... I think it's important that they continue to press if the seriousness of the situation isn't, sort of, acknowledged immediately."
He said Oranga Tamariki had already been moving away from using care-and-protection residences, looking more at smaller community-based residences.
"The problem is still the behaviour of staff, so regardless of whether they're in the larger care and protection residences now or they're in smaller community-based ones, it's the behaviour of the adults that is the issue."
He was "hugely disappointed" it had happened, particularly given the progress he said had been made over the past two and a half years, "not only in the residences but also out in the community".
"I'm confident that change is occurring, it is a big ship to turn around ... this doesn't help the cause," he said. "I think you'll notice that Oranga Tamariki hasn't quite been as prevalent in the news as it has been [previously] and that's because of the work that has been done."
However, he suggested it was better to do too much than not enough.
"I'd rather go hardout than sort of take the softly-softly approach and not really get to the bottom of things."