Emergency services were called to the Northfield prison after reports of a “medical emergency” about 11.30am on Friday involving inmate Wayne Morrison, 29.
On Saturday, Correctional Services Department chief executive David Brown said the critical incident involved an alleged assault by the prisoner on prison staff.
Of the five guards injured, two — a man and woman — received facial fractures.
“The prisoner involved in the incident was brought under control by responding staff,” he said. “In the course of the incident, a medical emergency ensued and the correctional staff applied immediate first aid to the prisoner and sought assistance from on-site medical staff.”
He said an ambulance was called a short time later and the prisoner was transferred to the Royal Adelaide Hospital.
An SA Ambulance spokesman said a man suffering a cardiac arrest was taken to hospital, as well as two other for more minor injuries.
Mr Brown declined to specify who suffered the heart attack.
“I cannot comment further on the circumstances or the cause of the medical emergency,” he said.
“What I can say is that, I personally, and the officers of my department, understand and take very seriously our responsibilities where a use of force is required to bring a dangerous situation under control.”
He said the prisoner’s next of kin had been notified of the incident.
“I would like to pass on my thoughts to the family of the prisoner who is now in a serious condition in hospital,” he said.
Mr Brown said he could not comment any further on what led to the alleged assault, the medical condition of the prisoner or whether his guards acted appropriately.
He said the five prison staff were treated for injuries — two suffered facial fractures, one had an injury to his shoulder and two others were assessed.
“I’m very concerned about the physical and mental health of my staff involved in this critical incident,” he said.
“My understanding is that the three staff who received medical treatment at the hospital were subsequently discharged from the hospital.”
Mr Brown said the incident happened while the prisoner was waiting in the admissions area of Yatala, waiting to appear via video-link to court.
He said SA Police’s Major Crime Investigation Branch was now investigating the incident.
“Correctional Services is co-operating fully with this investigation,” he said.
“This is clearly a very serious incident, the circumstances surrounding the incident and the medical emergency are now the subject of a police investigation.
Mr Brown said any CCTV footage of the incident would be provided to police and could form part of the investigation.
He said no weapons were involved.
An SA Police spokeswoman said Major Crime detectives were assisting with the investigation.