Inmates at Canberra's Alexander Maconochie Centre were treated for smoke inhalation after a detainee lit a fire in their cell.
Firefighters were alerted to the fire at the jail by an automatic alarm and a triple-0 call shortly before midnight on Wednesday, an ACT Emergency Services spokeswoman said.
Correctional centre staff had already extinguished the burning item by the time emergency services arrived and removed the detainee. The detainee did not require hospitalisation.
Paramedics treated several inmates for smoke inhalation but none needed to be taken to hospital for further treatment.
Firefighters conducted atmospheric testing at the jail into the early hours of Thursday morning.
Three pumpers, two commanders, one hazardous materials crew and crew with breathing apparatus were dispatched to the centre.