Police in Kent are also understood to have been alerted to the claims of “unnecessary use of force and the use of improper language” at Medway Secure Training Centre in Rochester.
It has been reported that staff punched and slapped some teenagers held at the facility and also allegedly boasted about using inappropriate techniques to restrain youngsters.
The centre, managed by G4S in co-operation with the Youth Justice Board since it opened in 1998, is a 76-bed facility for young offenders aged from 12 to 18.
The suspensions announced by G4S come after undercover filming by the BBC’s Panorama programme, which has yet to be aired.
The Times reported that it is alleged staff punched a youngster in the ribs and another was slapped several times on the head.
Staff were also alleged to have pressed heavily on the necks of young people, and staff tried to hide their actions by ensuring they were beneath CCTV cameras or in areas not covered by them.
G4S said it has referred the “serious allegations of inappropriate staff conduct” to Medway’s local authority designated officer, the YJB and the Ministry of Justice as Kent Police confirmed it was investigating.
Paul Cook, managing director of G4S children’s services in the UK, said: “I’m extremely shocked and appalled at the allegations that were presented to us, which clearly have no place in our business or any institution responsible for looking after young people.
“We received the allegations from Panorama to our press team on December 30, and all I have are written allegations at this time.”
CCTV has been secured relating to the dates given by Panorama, said Mr Cook, adding that they were treating the allegations with “utmost gravity”.
The YJB has suspended the placement of new youngsters at the facility, which would be “kept under review”, he went on.
Kent Police said in a statement: “Following a referral from the Medway local authority designated officer, Kent Police is investigating allegations that have been made regarding reports of abusive behaviour (physical and verbal) at a secure training facility in Medway.
“All necessary safeguarding measures have been taken and enquiries are ongoing.”
Youth Justice Board chief executive Lin Hinnigan said “immediate steps” were taken to safeguard those who are at the facility.
She said: “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.”