Armed robber Anthony John Smith has been moved to a single cell at Port Augusta prison after contraband was found in his shared cell.
The Correctional Services Department in South Australia said improvised weapons, including a sharpened screwdriver, along with mobile phones and substances believed to be drugs, were found on Wednesday.
Smith is serving a 30-year sentence for armed robberies and shootings.
"He's separated in an area of the prison where we place prisoners who are subject to investigation and we will now review the intelligence and the information that we've gathered in the course of this find and then we'll assess the placement of the prisoner," he said.
Opposition police spokesman Dan van Holst Pellekaan praised jail staff for finding the contraband but said the situation was alarming.
Certainly, knowing this prisoner's history, it is fair to ask why he was in a cell with somebody else, because it's very, very likely that he's shared his knowledge, his skills, his ability to acquire and hide this sort of material, with others," he said.
Correctional Services said the find made clear that jail protocols were working and police were investigating the matter.