Warning: this report discusses self-harm and contains the name of someone who has died.

Family members of two Western Australian children hospitalised over the weekend after self-harming in the state's notorious Unit 18 detention facility say they are scared for their lives.

The boys' relatives told the ABC that a report high-lighting the failures of staff to respond to suicide warnings of Indigenous 16-year-old Cleveland Dodd has exacerbated their fears.

On Friday a 17 year-old was rushed to hospital after self harming.

The boy's grandmother, his only carer, told the ABC she received a call but has not been told much about the incident or his welfare.

"They told me that he got admitted into hospital because of what he's done in his cell. I was worried and said, 'Well please, can you update me … can you ring me, let me know if he's okay?'"

Four days on from the incident, the elderly Carnarvon woman told the ABC she is yet to find out.

"I don't get a phone call from him to know what's going on... I'm in the dark, I don't know what's going on."

The mother of another Unit 18 detainee told the ABC her 16-year-old son was also hospitalised after self-harming in his cell.

She said she was only made aware of it when her son returned from hospital to Unit 18 and called her.

She provided the ABC an audio recording of a phone call with her son in which he said he was being treated "like an animal" in the Unit, which is located within maximum security adult prison, Casuarina.

"How does a mother cope with that? Cleveland's parents didn't even get to say goodbye to their kid. Is it going to be like that for mine? Or are they going to do something about it?"

Indigenous children are drastically over-represented in Western Australia's youth detention system.

Last Friday new Corrective Services Commissioner Brad Royce, who took the role when his predecessor Mike Reynolds was removed after Cleveland's death, said Unit 18 was "the safest place I can have them at the moment".

"Because as tough as this is, whatever I do, these kids are challenging, they have been through a lot long before they came in."But relatives of the two Unit 18 detainees say they are not assured," he said.

The 16-year-old's mother said: "Safest place? They've had a death in there... How can that be the safest place for a child?"

The WA Department of Justice told the ABC it could not provide a welfare update on the two young detainees due to privacy reasons, and that it would not comment on individual cases but that "young people are monitored and appropriate interventions are provided by staff".

The Department, asked if there had been any more suicide attempts since Cleveland's death, issued a statement in which it said it "formally reports verified Corrective Services data in its Annual Report and to the Productivity Commission's Report on Government Services, in addition to the oversight of other governance agencies and processes", but "(in) the interests of the small number of young people in detention at Unit 18, the Department is not publicly releasing information that may identify individuals or impact their future behaviours".

In August last year, when Unit 18 had only been operating for three weeks, under questions from Greens MP Brad Pettitt a representative for then Corrective Services Minister Bill Johnston revealed that between July 20 and August 8, there had been 13 self-harm incidents and three attempted suicides at the Unit.

Last week, more than 130 organisations and individuals prominent in the fields of justice, health and human rights urged Western Australian Premier Roger Cook to close Unit 18.

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