After the noose was found, he was classified as needing to be monitored every 15 minutes. But last Friday he was assessed as no longer at risk. According to claims from other inmates, they took the man for another mental health assessment on Saturday because of concerns about his welfare, but he was not reclassified. He died a day later. It was the second suicide since Karreenga was opened in September.

The 300-capacity unit was designed for restricted minimum security inmates, but modified to address a critical shortage of accommodation for medium security prisoners. The other two deaths were attributed to natural causes. However, one of those deaths may have been caused by a fall the man had within the unit weeks earlier and is under further investigation. The other suicide involved a man on remand earlier this year. The deaths at Karreenga have raised concerns about the unit and what was done to ensure its safety once it was reclassified, but also about a prison system which threatens to buckle under the weight of a record number of inmates.

There are more than 7000 people locked up in Victoria for the first time in history, a figure that has almost doubled since 2004. A spokesman for Corrections Minister Gayle Tierney said any death in custody was a tragedy, and acknowledged the delicate balance of reducing the strain on the prison system while ensuring the community was protected. Justice Paul Coghlan, the judge appointed by the state government to overhaul the bail system in the wake of the Bourke Street tragedy, said earlier this month that because "the tide of public opinion at the moment is going only one way" it was likely the prison system would be put under further strain. The surge of inmates created fissures in access to mental health treatment, according to Charlotte Jones, the principal manager at the Mental Health Legal Centre. "We have general concerns about what's happening, but particularly in this unit," she said.

There is a shortage of beds for those needing mental health treatment at the Thomas Embling Hospital, as well as people requiring assessment when withdrawing from substance abuse, she said. The Community and Public Sector Union, who represent prison workers, said Karreenga was not properly staffed for the mixture of inmates housed there. The state government will await investigations by the coroner and the Justice Assurance and Review Office before determining how to respond to the deaths. While prison deaths have increased considerably, the rate of deaths as a percentage of the inmate population has remained steady. Ms Tierney's spokesman said $57 million allocated in the last budget to improve access to health and mental health care in prison was also aimed at reducing recidivism.

Opposition Corrections spokesman Edward O'Donohue visited Karreenga on Monday - the day after the most recent suicide - but was not aware of any of the deaths until being told by Fairfax Media. He said his visit raised concerns about how the unit was suitable for medium security inmates. "Legitimate questions need to be answered about how the change of the prison from restricted minimum to medium has been handled and whether the infrastructure and staffing changes are appropriate," he said. Anyone needing support can contact Lifeline on 13 11 14 or MensLine on 1300 789 978. - with Adam Cooper