Specially trained prison officers had to be deployed to deal with a disturbance at a Kent young offenders' institute.
Kent Police said about a dozen teenage inmates threatened staff at Cookham Wood, in Rochester, Kent, on Monday.
The Prison Service said the incident lasted about eight hours.
In 2009 a report branded conditions at Cookham Wood "seriously unsafe". Officials said "significant improvements" had been made since.
A Prison Service spokesperson said: "At 1750 yesterday [Monday] 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 0200.
"No injuries were sustained by either staff or prisoners."
Cookham Wood was built in 1978, originally for young men, but was changed to meet the need for secure female accommodation at the time.
It was converted to a young offenders' institute in 2007/2008.
Inspectors said in 2009 too many inmates had been placed at Cookham Wood before it was ready following the facility's conversion.
At the time the report was released Prison Service said it did not "wholly accept that the prison was unsafe" but an action plan had immediately been put in place.
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