About 20 inmates at the Parkville facility were left without beds on Saturday night after their cells were trashed.

The riot came as an inmate at another prison facility attacked four prison officers, inflicting a serious neck injury.

Streets in Parkville were blocked on Saturday night as police dealt with the riot at the Youth Justice Centre.

Inmates at the juvenile facility destroyed security cameras, computers, and ripped the ceiling and walls apart during the riot, a prison source said.

It's believed the sprinkler system was also severely damaged after the group broke into one of the buildings and found a sledge hammer and shovel.

Computers were then thrown through the windows before the group climbed up on the roof and demanded junk food and a phone, the source said.

No youth justice officers or inmates were injured during the incident.

The riot only ended after police called in the dog squad.

The disturbance is believed to have been started by the same youth who triggered another riot on Thursday at the centre.

Community and Public Sector Union spokesman Julian Kennelly said officers had contacted the union about the riot, saying about 20 teenage inmates were involved and that the trouble centred on three residential units.

State government minister Richard Wynne condemned the rioting.

"The government is obviously really concerned about the events that occurred at the Youth Justice Centre last night, and, in fact, we have just put on 41 staff to ensure that the centre remains secure," Mr Wynne said.

Ambulance Victoria spokesman John Mullen said paramedics were initially called to the centre due to reports of youths on a roof and were on standby but were not required.

Department of Health and Human Services spokesman Mike Griffin said the department would "thoroughly examine" the circumstances leading up to the incident.

"The behaviour of these clients on Saturday was unacceptable and staff shouldn't have to tolerate it," he said.

Changes in policy could see the riot reported to the Youth Parole Board and may affect the parole eligibility of those involved.

Earlier this month, the Minister for Families and Children, Jenny Mikakos, announced that any youth inmate who assaulted a staff member or was involved in any other serious incident would have the matter reported to the parole board.

"We are developing a range of tougher measures to ensure we put a stop to this," she said on Sunday.

The centre has been plagued by violence in recent times.

In September, inmates and staff clashed for three consecutive nights and several juvenile offenders threatened staff and took control of part of the centre.

Amelia Banks, who lives nearby, said she heard a "police helicopter and a stream of emergency vehicles driving past with sirens blaring".

She raised concerns that the rioting was becoming frequent and worried about the safety of the children and officers inside.

"Whatever happens inside the centre clearly isn't working as the children who are in custody seem to be ready to riot at any given moment," Ms Banks said.

Alana Marzuke, who also lives nearby, said she saw up to seven police cars at the scene.

In the separate prison incident on Saturday night, four Port Phillip Prison officers were assaulted during a cell search, with one suffering a suspected serious neck injury.

The prison officers were searching an inmate's cell after visiting hours to check whether he had received contraband.

Paramedics were called to the Truganina prison at 7.10pm and transported the officer, aged in his 30s, to hospital. Ambulance Victoria confirmed the man was in a stable condition.

Mr Kennelly said the inmate was believed to be using drugs.

"If he has taken down four officers, we would suspect it was ice or something similar," he said.

The prison was placed in lock-down, Mr Kennelly said.

Three other prison officers were treated for minor injuries, and capsicum spray was used to subdue the prisoner.

He said Port Phillip Prison's contraband detection system was inferior to other prisons around the state and called for the private operator, G4S Australia, to upgrade it.

Mr Kennelly said contraband was rife in Port Phillip Prison, and this, added to overcrowding, was making it difficult and sometimes dangerous for prison officers.

"Port Phillip was built 20 years ago to house 600 inmates and it is now housing nearly double that," Mr Kennelly said.

Opposition corrections spokesman Edward O'Donohue said the justice system was in crisis.

"Further evidence overnight that the justice system in Victoria is in crisis with young offenders rioting at the youth justice centre, while prisoners at Port Phillip are attacking staff and reportedly taking ice," Mr O'Donohue said.

Prison operator G4S said it used "robust and proactive" security measures, which were having a positive impact on safety at the facility on a daily basis.

"We employ multiple strategies that are incorporated with modern systems to stop the flow and demand of contraband," G4S director Brett McMerrin said.

"G4S is dedicated to managing the safety and security of staff, prisoners and visitors."

- with Cameron Houston, Steve Lillebuen