Another man has died at Nottingham Prison, the Ministry of Justice has confirmed.
Darren Capewell, 37, died on Wednesday at the jail, which the Chief Inspector of Prisons warned was in a "dangerous state".
The MoJ said there would be an independent investigation by the Prisons and Probation Ombudsman.
Eight other inmates are thought to have killed themselves at HMP Nottingham in the past two years.
In January, Chief Inspector Peter Clarke issued an urgent notification to the government as it was the third time in a row prison inspectors found Nottingham Prison to be "fundamentally unsafe".
This followed the deaths of five men in four weeks between September and October.
Mr Clarke predicted "further tragedies" unless action was taken.
One prison officer told the BBC two suicide attempts a week were prevented at the jail.
The MoJ confirmed the death of Mr Capewell and offered its sincere condolences to his family.
Justice Secretary David Gauke said an action plan would soon be published following the "urgent notification letter" issued by Mr Clarke.
In a statement he said experienced staff had been sent to the jail and the number of prison officers had been boosted by "more than 100".
Nottingham's Independent Monitoring Board said it was "shocked and saddened" to hear of Darren Capewell's death.
It said in a statement: "Darren was well known to many prisoners, staff and Board members, and his death will affect many people in the prison community.
"We understand that support is being offered to those affected. We offer our condolences to those close to Darren and will await the results of the Ombudsman's enquiry."