Heavily armed police carrying shields have stormed Melbourne's maximum security prison in a bid to quell rioting prisoners.

Chaotic scenes erupted inside the Metropolitan Remand Centre in Ravenhall as masked inmates brandishing sticks, bashed in doors and windows, and lit fires.

Police at the scene said about 300 prisoners were involved in the demonstration which began at 12:20pm inside the prison on Tuesday.

Shots were heard coming from the facility just before 6:00pm but it was unclear whether it was tear gas being used or gunfire.

An estimated 200 staff were evacuated from the prison and all of the state's prisons went into lockdown as a precaution.

A drone was sent up to monitor the yard, with a police helicopter and a heavily armoured vehicle also on the scene.

Dozens of police officers were seen marching through the main entrance of the prison with riot gear.

Smoke was billowing from the prison, but has since subsided.

Corrections commissioner Jan Shuard said "a very large group" of prisoners had "created a big disturbance" at the facility.

She said the riot may have been related to a state-wide smoking ban in Victorian prisons, which is due to begin on Wednesday, but said that had not yet been confirmed.

Members of the critical incident response team outside the prison. ( AAP: Mal Fairclough )

"The situation is still being managed, until we can have a full debrief on it, we won't know how it got to this stage," she said.

"Until I get a full debrief, I can't speculate about how it all came about."

Earlier a group of prisoners breached a secure inner perimeter of the remand centre, but Ms Shuard said most prisoners had been brought under control.

"We've got a large proportion of the prison locked down now, but we still have too many out and until we have them under control the number [involved] is too hard to be determined."

She said the perimeter of the prison had been secured by police and there was no threat to public safety.

Community and Public Sector Union acting secretary Catherine Davies said "all of the staff have been accounted for and there's been no injuries".

A fire also broke out at Port Phillip Prison, in nearby Truganina, but Corrections Victoria said it was unclear if it was related to the events at Ravenhall.

The Metropolitan Remand Centre is a 1,000-bed facility, 24 kilometres west of Melbourne's CBD.

Heavily armed riot police carrying shields are attending a demonstration at the Metropolitan Remand Centre in Ravenhall. ( ABC News: Peta Carlyon )

Prison smoking ban to be introduced on Wednesday

Ms Shuard said corrections had been preparing for 18 months to prepare for the introduction of the smoking ban.

"We've been working diligently through a whole range of activities and plans to be able to manage [the] prison population in the lead up to our non-smoking in our prisons," she said.

"These people are on remand ... so they are the people that won't have come as much on the journey with us around ceasing smoking, because they are newly arrived people in our system."

About 84 per cent of people going into the state's 14 prisons smoke and about 1,300 prisoners, or 20 per cent of the prison population, have attended quit programs up until the end of May.

Melbourne Metropolitan Remand Centre, is around 24 kilometres from Melbourne's CBD. ( Google Maps )

Chief executive of the Victorian Association for the Care and Resettlement of Offenders, Carol Nikakis, said most prisoners seemed to have accepted the ban.

"[Corrections Victoria] have been very active in providing alternative therapies; they've also used the Quit program within the prison to assist people to adjust to the news," she said.

"I think it's D-Day now and people are thinking what am I going to do without my cigarettes, but they have been well prepared by corrections."

Ms Shuard said the department would review how the situation unfolded.

"We will thoroughly review how this came about, how we responded to it and what we might need to do in the future," she said.

"If criminal acts have occurred within the prison today that would be up to Victoria Police to pursue any charges."