An outbreak of Covid-19 has been confirmed at a jail in an area where the virus more than doubled in a week.
The Ministry of Justice said new infections have sprung up at HMP Manchester but would not confirm how many.
Cases in the Strangeways area of the city rose from 44 to 105 in the week to 17 February.
A Prison Service spokesman said it had taken "precautionary measures" and was monitoring the situation.
He added: "Our priority is to limit the spread of the virus and protect the lives of those who live and work in our prisons."
Manchester City Council said it was working with Public Health England and the Ministry of Justice "to monitor any new cases and prevent the virus from spreading further."
Another prison in neighbouring Salford was also dealing with an outbreak.
A spokeswoman for HMP Forest Bank at Agecroft said: "A small number of staff and prisoners on five of the sixteen wings within Forest bank recently tested positive for Covid-19.
"The current situation is well controlled and under constant review."