Emergency services are at Yatala Labour Prison, Northfield in response to a suspicious package.
Police, paramedics and MFS crews were called to the prison about 9am on Friday 7 December.
One person has been taken by ambulance to the Royal Adelaide Hospital in a stable condition.
MFS are currently dealing with the HAMZAT incident and further information will be provided as it comes to hand.
Anyone with information that may assist the investigation is asked to contact Crime Stoppers on 1800 333 000 or online at www.crimestopperssa.com.au