It is one of two active probes into alleged abuses of children in Victoria's youth detention system.

Both have been ordered by the state's new Commissioner for Children and Young People, Liana Buchanan, who began the role in April. She ordered the first probe in her first week as Commissioner for Children after a 13-year-old boy fractured a "limb" in an incident with a staff member at the Parkville youth residential centre.

In the wake of Monday's evidence of horrific abuses in the Northern Territory on the ABC program Four Corners, Ms Buchanan said: "Any closed environment with vulnerable kids needs to be scrutinised."

The Victorian government said the use of isolation as a punishment was "expressly prohibited" under state law, but could be used "when all other reasonable steps" had been taken to prevent the inmate from harming themselves, others or property.

Ms Buchanan said the Parkville incident began with  a confrontation between two young inmates.

"Two kids were on the verge of starting to have a blue," she said, "and a staff member intervened to restrain. That was enough for me to look at how it happened and what training could prevent that inappropriate restraint. What factors led to it?"

The other inquiry - which includes investigating the young inmate in solitary confinement - is broader, and will include issues of "isolation, separation and lockdowns" at both the Parkville and the Malmsbury youth justice centre.

"I was concerned after getting reports of the number of lockdowns, not because kids have been bad or pose a risk," she said, "but for operational reasons. I was also concerned about some examples where children seemed to be isolated for what appeared to be to be for a long time. They don't call it solitary confinement but the effect is the young person is kept away from other young people in an isolation unit on their own."

In February, Victorian laws around children in detention were changed, making it compulsory for the commission to get all reports of "serious" incidents in the state's youth prisons. Ms Buchanan said despite the two current investigations, Victoria was no Northern Territory.

"I am confident that the kind of state-sanctioned abuse that we have witnessed in the Northern Territory is not taking place in our centres. We have tried in Victoria to put in place a reasonably humane approach with a clear focus on rehabilitation, not punishment." She said in general youth incarceration rates and youth crime – despite perceptions around the Apex gang  – were low.

"Victoria has a low imprisonment rate and a low crime rate for youth and it shows we don't have to lock kids up to respond to crime," said Hugh de Kretser, the executive director of the Human Rights Law Centre. However he said indigenous Victorian children were still eleven times more likely to end up in youth justice centres than non-indigenous children, which was a "disgrace."

In 2012 a 16-year-old Aboriginal boy was held in solitary confinement for nearly four months in an adult jail while under a government child protection order. He had attempted to escape from Parkville. In 2013 the Victorian ombudsman found that the increasing instances of children being held in adult jails breached the state's human rights act.

Restraint chairs and spit hoods – as seen on Four Corners at the Don Dale youth detention centre, near Darwin - are not used in Victorian youth detention.

Human rights advocates today repeated calls for Australia to ratify the United Nations' optional protocol to the convention against torture, which mandates independent inspections on detention centres. Australia is one of only 17 countries to have signed but not ratified the protocol.