Oranga Tamariki chief executive Sir Wira Gardiner said he was "deeply concerned that excessive force looks to have been used against children and young people in our care".
This morning he told Mike Hosking on Newstalk ZB "a number of staff" were stood down yesterday.
He said given there appeared to be "more than necessary force to restrain a child" they launched their own investigation.
"We have a protocol with police, the child protection protocol, where we bring in police to investigate the level of force and whether an assault has occurred.
"We stood down a number of staff yesterday.
"We've appointed a social worker to make sure the child, or young person involved, was okay."
Asked by Hosking whether he was confident he could get Oranga Tamariki out of its "mess", Gardiner said it would be possible, but with a bit of work.
"If I might use an analogy, it's like turning a large container ship.
"It'll take time, it'll take commitment, it's not a resourcing issue.
"I think we need to look at the way we do some practices, we probably need to change the culture of what we do, but yes it's possible."
He said one of the main ingredients in changing the tide was getting the public's support.
"Because every day hundreds of my staff on the front line are facing enormous challenges which come from dysfunctional families, a whole range of challenges as we deal with these kinds of situations.
"The main thing is, I've told my staff to use their experience and judgment to the best of their abilities, if we make a mistake, fess up and let's fix it."
The video, published on Newsroom, shows a boy aged around 13 in one of the state child protection agency's Care and Protection Residences being tackled, held on the ground by three staff members, his face pushed into a wall and arms twisted behind his back.
Another video shows him being placed into a headlock and also thrown to the ground.
The whistleblower told Newsroom such residences were for the country's most vulnerable young people, who hadn't committed a crime, were not being held as punishment and often came from years of violence and trauma with complex needs.
Speaking to the social services and community select committee on Wednesday Gardiner revealed there had been 223 holds applied in residences in 2019 and 170 in 2020.
There had been 12 injuries recorded in the past four years, including one serious.
Gardiner said they had determined these residences were "not conducive to good care".
They had plans to build 10 smaller facilities across the country in partnership with iwi over the next two to three years, he said.
They would have fewer children, more staff, and allow for the care and attention needed, he said.
He could not say when the current residences would be shut down.
Regarding the latest incident, Gardiner praised the whistleblower and said he would have "done the same".
There were CCTV cameras monitoring these facilities and the normal processes should have required the incident be reported.
"That is one issue we will be looking at, why that did not happen."
They were also concerned given it was not reported that the practice could be more widespread.
A link to the video had been sent to staff across the country to highlight it was not appropriate action, he said.
Speaking before the committee Davis said CCTV footage was deleted after a certain period of time, and conceded footage of the incidents in question could have been deleted.
More generally Davis outlined the major works under way at the embattled child protection agency, vowing the series of reviews and expert panels would not "just be lip service".
A review from an expert panel appointed in January due today had been delayed two weeks, Davis said. He would provide a response to it by August.
He noted comments recently from former National Social Development Minister Paula Bennett on the need to devolve functions to Māori when she was in office, and the difficulties in doing so.
Davis said he was committed to making the changes necessary.
"Yes mistakes have been made, yes we need to devolve. It is clear the system is broken, but many people working inside the system are not. They care for the children they protect and go above and beyond what system allows.
"I hope we can finally live up to name Dame Naida Glavish gave us, Oranga Tamariki."
