Police will be out in force to ensure Melburnians are wearing a mask when they leave their house as Victoria continues to record high coronavirus numbers.

The new mandate for Melburnians to mask up has come into effect and police have warned they will be handing out fines where necessary.

As of Thursday residents of metropolitan Melbourne and Mitchell Shire who leave the house for one of the four allowed reasons without a mask could face a $200 fine as the state battles a second wave of coronavirus.

In a statement police said they will exercise discretion over the next week with regard to the rule, but there will not be a lot of room for leniency.

"We understand that for many people this is a significant adjustment," the statement read.

But officers will fine those who flout the new rule without good reason.

"That said, we do expect people to follow the Chief Health Officer's directions and will not hesitate to issue fines to people who are obviously and blatantly showing a disregard for community safety by failing to wear a mask."

If a person has a mask and refuses to wear it when requested, that person can expect to be issued with the fine, a police spokeswoman said.

"Similarly, if a person persists with entering a supermarket when requested not to do so due to the absence of a mask then that person can expect to be issued with a fine."

Victoria's new mask rule comes as the state recorded Australia's highest daily figure of 484 new cases and two more deaths, both male aged care residents in their 90s.

There are now 45 outbreaks in aged care facilities across the state, with 383 staff and residents testing positive.

An outbreak at St Basil's Homes for the Aged in Fawkner has grown to 69 cases in staff and residents, while 54 people at Estia Health have contracted the disease.

A new cluster has also emerged at Kirkbrae Presbyterian Homes in Kilsyth, with two staff and one resident testing positive.

Meanwhile, a second prisoner from the Metropolitan Remand Centre returned a positive result on Wednesday after being tested on Monday.

A spokeswoman from Corrections Victoria said there was no connection between the latest case and a previous positive case at Metropolitan Remand Centre last Friday, or a prison officer at Ravenhall Correctional Centre who tested positive on Tuesday.

Ravenhall has been placed into a total lockdown along with five other prisons including Hopkins Correctional Centre, Langi Kal Kal, Barwon Prison, Fulham and Loddon.