A mental health unit where two girls died in two months is to close, a watchdog has said.
The Care Quality Commission (CQC) rated Middlesbrough's West Lane Hospital as inadequate and said patients were at high risk of "avoidable harm".
It followed the deaths of 17-year-old Christie Harnett in June, and Nadia Sharif, also 17, who died on 9 August.
The trust said it was taking action to minimise the impact of closure on patients and their families.
A CQC spokesperson said it had taken "urgent action" to close it.
They added: "Inspectors are currently working closely with the trust and NHS England who are arranging appropriate alternative care and support for the young people affected, in a safe and timely manner.
"CQC's priority is always the safety and wellbeing of people using services and has taken this action to ensure they are protected and kept safe from avoidable harm.
"The report from the most recent inspection in August will be published in due course. Any action taken by the CQC is open to appeal by the provider."
The CQC said the Holly Unit at West Park Hospital and Baysdale Unit at Roseberry Park, which are operated by the same trust and offer similar services, were "unaffected".
It said the closure notice followed "continued concerns identified at earlier inspections" of West Lane.
The CQC said 11 young people were in the unit when it was inspected on Wednesday. This is thought to be the first time the CQC has closed an NHS children's mental health hospital due to failures.
Concerns were first raised last November about West Lane Hospital's Westwood Centre, which offers secure adolescent inpatient accommodation.
They centred around claims staff used techniques for moving patients which were "not taught and not in line with trust policy".
Admissions to the hospital were temporarily suspended following Christie's death.
On Thursday, it was revealed 13 staff suspended over the alleged ill-treatment of patients were still working for the trust.
The two girls' families called for action to be taken to prevent further deaths.
Christie had been in care facilities for two years and had a number of mental health issues, including hearing voices, which led her to self-harm and make multiple attempts to take her own life.
She was found dead after telling staff at the hospital she wished to take a bath.
Following her death, her stepfather Michael Harnett alleged that during her time there workers restrained her without warning, illegally strip-searched her and allowed a male member of staff to be present while she was naked.
Mr Harnett added that in the months before her death, his daughter "should've been listened to" rather than repeatedly being discharged by different care facilities.
Nadia had autism and mental health issues and had been cared for for four years.
Her father Hakeel Sharif said following her death: "I think the care wasn't there, it should have been 24 hours the way she was doing."
Mr Sharif said improvements needed to be made "very quickly" and it was "not safe for the kids being there".
"They need to sort it out really fast, we don't want to lose any other lives," he added.
Middlesbrough Labour MP Andy McDonald said it was a "catastrophic failure by the trust" and he was concerned where those who needed help would now go.
"But the decision has been made and presumably the CQC and the trust have decided that West Lane just cannot be made safe, so this is a huge issue, it is a systemic failure, and of course there's going to be a number of inquiries now," he said.
A Department of Health spokesperson said patient safety was "paramount" and all providers of NHS mental health services "must meet the same high quality and safety standards, with rigorous oversight by the Care Quality Commission."
Colin Martin, chief executive at Tees, Esk and Wear Valleys NHS Foundation Trust, said: "We understand that this is extremely difficult for the young people at West Lane Hospital and their families.
"They deserve to be cared for in a safe, high quality environment and we are sorry that the care we provided did not meet the standards we would expect.
"Our immediate focus is minimising the impact that the closure may have on our patients and their families.
"We are committed to working closely with patients, families, staff and NHS England to work through timescales and to make sure we to provide a smooth and safe transition for patients to alternative services."