Restrictions have been tight at the South Nowra facility since June with no face-to-face visitations allowed.

Additional restrictions have also been put in place to restrict inmates' movements.

Inmates are being restricted to their cells for long periods, and it's understood only essential services are being allowed, such as undertaking court appearances via audio visual links, health appointments or treatment.

A number of internal programs have also been restricted or stopped.

It is understood a number of inmates have been transferred to South Coast from the troubled Parklea prison, which has recorded 31 COVID cases.

Read more: NSW records four deaths, nearly 1300 new COVID cases

The Bathurst Correctional Centre in the Central West has seen an additional two COVID-19 cases confirmed by Correctives Services NSW. The two new cases take the total cases in staff at the Bathurst facility to eight after six infections were confirmed late Sunday. All the cases are now in isolation.

COVID cases have also been detected in two Hunter Valley prisons from an outbreak that started in Parklea in Sydney and cases are no also in Junee.

Earlier this month a staff member at the South Nowra jail who was subject of contact tracing, after their partner was a possible contact, has tested negative for COVID-19.

A Corrective Services NSW spokesperson said "all NSW prisons are continuing to take extra precautions after inmates, who may have been exposed to the virus, were recently transferred out of Parklea Correctional Centre".

"For the past 18 months, Corrective Services NSW has effectively managed COVID-19 risks and prevented transmission of the virus between inmates and staff in NSW prisons," the spokesperson said.

Read more: Lessons from a COVID-19 outbreak

"But like hospitals, schools, aged care facilities and police stations and with the significant number of cases in the community, and the transmissibility of the Delta strain, COVID-19 has now entered our correctional system.

"We are introducing rapid antigen screening across the state for staff and inmates to boost our frontline defences.

"The safety of all staff and inmates is our number one priority while we continue to follow the expert advice of NSW Health and JH&FMHN in our decision-making processes."

The Justice Health and Forensic Mental Health Network, which is responsible for health issues within NSW jails, has been contacted for comment.

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Meanwhile, the Public Service Association, the union looking after prison officers, has urgently called for more "jabs in jail" saying some officers are still waiting to get vaccinated even as COVID-19 case numbers begin to seriously test their efforts to keep NSW's jails virus-free.

The association has called on Justice Health to reinstate the on-site vaccination rollout, saying another round of workplace vaccinations for prison officers was urgently needed to make sure there isn't mass spread inside any prison.

Justice Health and Forensic Mental Health Network (the Network), which coordinates such work in the prison system, said the first phase of vaccinations had been completed and would be "going back into Correctional Centres again in the coming weeks to provide another round of AstraZeneca vaccinations".