Police were alerted to the claims of “unnecessary use of force and the use of improper language” as a result of a BBC Panorama investigation into Medway Secure Training Centre (STC) in Rochester that is yet to be broadcast.
It is understood the allegations include staff punching a young person in the ribs, another being slapped several times on the head, and staff pressing heavily on the necks of young people.
There are also claims that staff at the STC, which is run by private firm G4S, used unnecessary restraint techniques and that staff boasted of using a fork to stab one young person in the leg, and making a young person cry uncontrollably.
A spokesman for Kent Police said: "Following a referral from the Medway Local Authority Designated Officer (LADO), Kent Police is investigating allegations that have been made regarding reports of abusive behaviour (physical and verbal) at a secure training facility in Medway."
Youth Justice Board (YJB) chief executive Lin Hinnigan tweeted that action has been taken to protect children at the unit, which has 76 beds for young offenders aged 12 to 18.
Lin Hinnigan: "...immediate steps have been taken to safeguard those who are at Medway STC."
— Youth Justice Board (@_YJB) January 8, 2016
In a statement, YJB chief executive Lin Hinnigan added that the safety and wellbeing of children and young people in custody is paramount for the YJB.
"We have increased our own monitoring activity and the presence of our independent advocacy service, delivered by Barnardo's. All of the staff identified in the allegations have been suspended by G4S, which runs the STC.
"Kent Police are reviewing each alleged incident and an investigation is under way. We are working closely with them and the other agencies involved, so it is not appropriate for us to comment further on the allegations."
Paul Cook, managing director for G4S children’s services in the UK, said the allegations are being treated with "the utmost gravity".
"We take any allegations of unacceptable or inappropriate behaviour extremely seriously and are giving our full support and co-operation to the LADO and the police as the investigation moves forward,” he said.
“The police and LADO are the appropriate independent authorities to conduct the initial investigation into the allegations and once that investigation has concluded, we will agree with the Ministry of Justice and YJB whether further independent review or investigation is required.”
“We continue to focus on the care, wellbeing and education of the young people at the centre, which is our primary objective.”
The allegations come less than a year after it emerged that young people at a G4S secure training centre in Northamptonshire had been subjected to degrading treatment and racist abuse from prison officers.
An inspection of Rainsbrook Secure Training Centre (STC) in Rugby, which is run by G4S, found that there had been "serious incidents of gross misconduct by staff", including some who were in positions of leadership.
Following this, in September, G4S lost the contract to run Rainsbrook STC, but was awarded the contract to continue running Medway for a further five years.
Gareth Jones, chair of the Association of Youth Offending Team Managers, tweeted advice for any parents with children in custody who are concerned by the latest allegations.
Shocked at allegations in Medway. Any parent/carer worried about their child in custody should speak with their YOT officer who can help
— Gareth Jones (@AYMChair) January 8, 2016
Carolyne Willow, director of children's rights campaign group Article 39, said: “If these allegations are proven to be true, there can be no denying that child abuse has been endemic in this G4S-run prison.”
“These are not isolated allegations; there have been serious concerns about secure training centres from the start. An independent child abuse inquiry must be established to investigate the full extent of mistreatment within the centres, and the mechanisms available to children to report their concerns and seek outside help."
