Three men have been arrested on suspicion of child neglect by police investigating allegations of abuse and mistreatment of youngsters at a facility run by private security group G4S.
Kent Police said the trio, who are all in custody, will be interviewed later on Wednesday following claims aired on BBC's Panorama programme this week.
Undercover footage showed staff allegedly mistreating and abusing inmates at Medway Secure Training Centre in Rochester, and allegedly boasting about using inappropriate techniques to restrain youngsters.
A Kent Police spokesman said: "Officers investigating reports of abusive behaviour alleged to have taken place at a secure training facility in Medway have arrested three men on suspicion of child neglect.
"The Kent Police investigation was launched following a referral from the Medway Local Authority Designated Officer. The men are currently in custody and will be interviewed later today."
G4S announced it had sacked four members of staff at the 76-bed centre, which is for young offenders aged 12 to 18.
Three other staff identified in the allegations were suspended pending further investigation, and one other person was removed from operational duty as inquiries continue.
G4S referred the "serious allegations of inappropriate staff conduct" to Medway's local authority designated officer, the YJB and the Ministry of Justice.
The Youth Justice Board has said it was working closely with Kent Police and had taken "immediate steps" to safeguard those at the facility.
Paul Cook, managing director for children's services at G4S, said: "We fully support the action of Kent Police this morning and we continue to provide police officers and the local authority with full access to Medway Secure Training Centre and the centre's records, including CCTV footage.
"There is no place in our business for the conduct shown on the BBC's Panorama programme on Monday night. This morning's arrests send a strong message that any allegations of wrongdoing will be thoroughly investigated and we are grateful to the police for their swift action in this case.
"We will work with the police and local authority to keep our own actions under review in light of today's developments.
"We will keep families and other professionals working with young people informed of developments as we are asked to do so. We are committed to a complete review of how this occurred and how we can ensure it doesn't happen again."