An 84-year-old man has become the first British prisoner to die after contracting coronavirus.
The inmate, named by sources as convicted paedophile Edwin Hillier, was serving at HMP Littlehey in Cambridgeshire.
Hillier, who reportedly had underlying health issues, died in hospital on Sunday, having been moved there from the category C male sex offenders' prison.
A second serving UK prisoner, a 66-year-old male inmate at HMP Manchester, died in hospital on Thursday after contracting coronavirus.
He had been receiving end-of-life care for an underlying health condition before he tested positive for Covid-19.
A Prison Service spokesman said: "An 84-year-old prisoner at HMP Littlehey died in hospital on March 22.
"A 66-year-old prisoner at HMP Manchester died in hospital on 26 March."
Former school caretaker Hillier was jailed at St Albans Crown Court in 2016 for sexually abusing two girls in the 1970s.
The spokesman said that in both cases, as with all deaths in custody, there will be an independent investigation by the Prisons and Probation Ombudsman.
As of Wednesday, 19 inmates had tested positive for Covid-19 across 10 jails and four prison staff had tested positive for the disease across four jails.
Three prisoner escort and custody services staff have also tested positive for Covid-19.
The Prison Service said robust contingency plans have been put in place at its facilities in consultation with Public Health England and the Department of Health and Social Care.
It added that prisons are well prepared to take immediate action wherever cases or suspected cases of Covid-19 are identified, including the isolation of individuals where necessary.