Four offenders at a youth detention centre were taken to hospital after a suspected drugs-related incident.
Six other young people being held at Hydebank Wood College in south Belfast required treatment on site.
Prison staff are understood to be investigating a suspected drugs link to the incident on Friday evening.
None of offenders involved was in a life-threatening condition.
The four who were taken to hospital returned to Hydebank after treatment.
A Northern Ireland Prison Service spokesman said: "Four young people from Hydebank Wood College were taken to hospital after becoming unwell.
"Following medical examination they returned to the college.
"As a precaution, a further six students received medical attention on site.
"None of those involved faced life-threatening conditions.
"Hydebank Wood is operating as normal and the Prison Service will be fully investigating the circumstances of the incident."