Last month's riot at Ravenhall, which provoked an armed response, led to the loss of personal information relating to guards and their families. Credit:Pat Scala. Images courtesy of ABC and Channel Seven The riot came just a day before a smoking ban comes into force across Victoria's 13 prisons. Prisoners have not been able to purchase cigarettes at the prison canteen since June 12, which is understood to have caused tension between those with tobacco and those without. As heavily armed members of the Special Operations Group and Tactical Response Unit battled to regain control, some prisoners hijacked a tractor, while others hurled a golf-buggy onto a bonfire. Plumes of smoke shrouded the sky above the prison for most of the afternoon.

Tear-gas was used to repel more than a dozen prisoners who had smashed their way into the control room. Images courtesy of ABC and Channel Seven Up to 300 inmates are believed to have been involved in the riot, but many surrendered to police or prison staff as the situation escalated. By nightfall, about 100 prisoners were still on the lose, according to a police source.

About 30 police entered the facility through the main entrance just before 9pm. A short time later, whoops and cheers could be heard coming from inside the centre. Another fire was reported at the high-security Port Phillip Prison, but was quickly contained. Images courtesy of ABC and Channel Seven Corrections Commissioner Jan Shuard conceded the riot was one of the worst in the state's history, but said all prison staff were safe and accounted for.

"There is no threat to community safety," she said. She confirmed several small fires had been lit in the prison, which were quickly contained. "As part of our response where there is an incident at one of our prisons it is a natural response that we will secure the rest of our prisons," she said. Evacuated staff stand outside the prison. Photo: Pat Scala

Ms Shuard said Corrections Victoria would proceed with the the smoking ban at the 1000 bed facility, despite concerns among prison staff of further rioting. Several sources confirmed there had been mounting tension at several other prisons in the lead-up to the introduction of the tobacco ban. When Queensland introduced a smoking ban in 2013, the state recorded short-term spike in attacks on prison guards, particularly during the period between when canteens stopped selling tobacco products and the ban was implemented. Police gather outside the prison. Photo: Pat Scala

A police helicopter hovered over the prison for several hours, shining a spotlight on the area. Just before 10pm, a lone ambulance entered the prison through the reinforced doors but its sirens were not blaring. About an hour later it emerged from the building and drove away from the site, although it is not known whether anyone was taken to hospital for treatment. Community and Public Sector Union spokeswoman Catherine Davies confirmed that no Corrections staff had been injured. "I'm not sure what caused the situation to escalate, but I'm aware of increased tensions because of the smoking ban."

She said the union would make a further statement, when prison staff had been de-briefed and the damage assessed. The Metropolitan Remand Centre is Melbourne's main holding facility for men on remand and is understood to be at full capacity. After opening in 2006 with 600 beds, the prison's capacity was increased last year to 1000 following a $65 million extension. The prison is divided into a dozen cell blocks, with a fenced corridor running through the centre of segregated yards.