Nine more prison officials have tested positive for the coronavirus, the Department of Correctional Services confirmed on Friday.
This brings the total number of confirmed cases at correctional centres to 94, spokesperson Singabakho Nxumalo said in a statement.
Kutama Sinthumule Correctional Centre, a private facility in Limpopo, has reported its first case, while the Warm Bokkeveld Prison in the Western Cape registered four.
East London and Worcester correctional centres each recorded two new cases.
Nxumalo said all 27 inmates tested at St Albans Correctional Centre in Port Elizabeth, where an official this week was confirmed to have contracted the coronavirus, had tested negative.
"As a result, East London [Correctional Centre] remains the only correctional facility, amongst the country's 243 centres, to have inmates testing positive for Covid-19," he said.
"Screening of officials and those accessing Department of Correctional Services premises remains in force as a measure to prevent possible transmission of the virus. Decontamination is also underway where positive cases have been reported."
A total of 29 officials in the Eastern Cape, seven in the Western Cape, one in Limpopo and one at the department's head office in Tshwane have tested positive.
Confirmed Covid-19 cases at the East London Correctional Centre remain at 56, with no new cases among the inmates since Wednesday.