During a routine check of cells in the High Risk Management Correctional Centre, staff located a 23-year-old with critical injuries, at around 7.30am on Saturday.

The man was in single-cell accommodation at the time, a Corrective Services spokesperson confirmed.

Corrective Services Investigation Unit (CSIU) are investigating the death, believed to be non-suspicious. 

A report is being prepared for the Coroner.

Meanwhile, Corrective Services NSW has praised staff who suppressed an incident at the Correctional Centre on Sunday afternoon.

Just before 4pm, six inmates returning to a yard began fighting with each other. One of the men produced a gaol-made weapon and began stabbing another with it. 

Two officers in the area immediately intervened and broke up the fight, disarming the inmate.  Additional staff attended and tear gas was used.  

Five of the men involved were handcuffed and segregated. The sixth man suffered stab wounds and was taken to Goulburn Base Hospital. His injuries were believed to be non-life threatening.

"Fortunately all our staff are well trained to deal with inmate unrest," Assistant Commissioner Kevin Corcoran said. 

"I congratulate the Goulburn officers whose response was nothing short of courageous." 

An investigation into the incident is under way. 

On Saturday, as a result of continued security and contraband crackdown, five mobile phones and a small quantity of drugs were located during an intelligence-based search of a cell.

Police were notified and the phone’s contents were to be analysed to determine appropriate charges.