Sister 'broken' by Aboriginal inmate death

The sister of an indigenous man who died after a violent altercation with five guards at a South Australian prison says she is "broken" by the death.

Police say the 29-year-old, unnamed for cultural reasons, died early on Monday morning at Royal Adelaide Hospital where he had been in a serious condition since the incident at Yatala Labour Prison on Friday.

"We said goodbye to my brother early this morning," his sister Toya Aroha posted on Facebook.

"I walked from the hospital to the steps of parliament and just sat there all morning till the sun came up...

"I though [sic] that maybe I had the courage to stay until Jay Weatherill came out and could ask for justice...but I just ended up breaking down.

"I can't be strong. I am broken. We are broken."

Earlier, she had referred to her brother as a "non-violent fisherman and artist".

SA police's correctional services unit and Major Crime Detectives are investigating the circumstances of the death.

Police are also preparing a report for the state coroner.

Department for Correctional Services chief executive David Brown said in a statement his thoughts were with the man's family.

"I want to again acknowledge the pain the family must be experiencing," he said.

"I want to reiterate that any death in custody is of deep concern and I again want to extend my condolences to the family of the deceased.

"Every possible action is taken by staff to identify and, wherever possible, prevent deaths in custody."