A prison riot led to an eight-hour stand-off between guards and teenage inmates.
The incident at HM Cookham Wood in Borstal began just before 6pm on Monday and was not brought under control until 2am the following morning.
Police have confirmed 13 inmates, who are aged 16 to 18, gained control of one of the wings and threatened staff.
A police spokesman said an intelligence officer was sent to the scene but the incident was dealt with by prison staff.
Five fire crews were on stand-by outside the prison after the youths threatened to set alight to the wing, but they were not needed and were stood down at 2.30am.
A Prison Service spokesman said: “At 5.50pm yesterday (December 27) there was an incident of concerted indiscipline at HMYOI Cookham Wood. Specially trained prison officers were called to the prison and all the prisoners were returned to their cells at 2am. No injuries were sustained by either staff or prisoners.”
The latest disturbance follows an all-day riot in October, in which thousands of pounds of damage was caused to the education block.