Firefighters will keep a close eye on a massive blaze in Victoria’s west as investigators look into the cause of another fire.

The more than 22,000-hectare Bayindeen fire, west of Ballarat, was contained as of Thursday a week after it started.

Residents of nearby communities including Amphitheatre, Avoca, Bayindeen, Beaufort, Elmhurst, Raglan and Waterloo were told it was safe to return, although authorities warned of continued localised fire and smoke.

Country Fire Authority deputy chief Garry Cook said while some firefighters were stood down on Thursday, crews would continue to monitor the Bayindeen blaze for any flare-ups.

“You can have a tree that might smoulder a kilometre in from the edge and it might flare up there,” Mr Cook told AAP on Thursday night.

“Sometimes, you’ll get root systems in old stumps and things like that (that will) smoulder under the ground and then they’ll re-emerge in a couple of weeks.

“That’s why we’ll continue to have patrols and not leave that fire unattended in any way, shape or form.

“To say that 20,000 hectares will be completely extinguished is just not something we could actually achieve.”

Impact assessments for the blaze were completed, with six homes destroyed, Mr Cook said.

Fire crews were assessing trees in the Bayindeen fire zone to determine what ones were hazardous.

Investigators were also looking into the cause of another fire at Dereel, about 30km south of Ballarat, which ignited on Wednesday during extreme conditions and threatened more than 100 homes.

It was being treated as suspicious given there was no dry lightning in the area, or machinery operating at the time.

An advice message said that fire posed no threat to residents as of Thursday.

The Country Fire Authority was preparing for more dangerous conditions on Wednesday, with early indications suggesting several districts would have very high fire danger ratings, Mr Cook said.

A high pressure system was expected to lead to high temperatures in Victoria on Wednesday before a wind change.

“How hot it is, how strong the winds are and the timing of those things – it’s too early (to say),” Mr Cook said.

“As we know more about that we’ll start our preparations both for the fire services and more broadly the messaging to the community about what we can expect.”

The bureau is predicting below median rainfall for most of Victoria including Melbourne in autumn.

Source: AAP