The ministry says the inmates were exposed to the virus before going into custody.
They are being managed appropriately to avoid any chance for the virus to spread to the wider prison population, it says.
It says there is no evidence of transmission at this stage.
Nationwide, 67 percent of prisoners have received their first dose and 50 percent are fully vaccinated.
The Corrections Department has been approached for the actual numbers of those in custody with Covid-19.