Police,along with other agencies,were still investigating its cause,he said.

Heffernan said the last resort for people caught in the fires were Neighbourhood Safer Places and designated fire refuges.

“Fires will become very uncontrollable very quickly and no homes are designed to withstand those catastrophic conditions,” he said.

“So if your plan is to leave early,you are requested to do so this evening or by tomorrow morning. I would not leave any later than lunchtime because those weather conditions will become quite nasty from 12pm onwards.”

Premier Jacinta Allan said six residential houses and 10 outbuildings had been destroyed in western Victoria since Thursday,and that number could change.

“We do know this remains a very active fire,as a consequence,there remains that Not Safe to Return emergency alert out to the communities around Amphitheatre,Elmhurst and Mount Cole,” she said.

Allan said Wednesday’s catastrophic fire danger had been extended to Horsham,Stawell and Warracknabeal,and that district was now being notified to upgrade its preparations.

She said emergency services were closely monitoring conditions in south-western Victoria,including Colac and Warrnambool and through to the South Australia border.

That region is under an extreme fire danger alert but could be upgraded later on Tuesday,the premier said.

The watch-and-act warning is in place for residents of Amphitheatre,Bayindeen,Ben Nevis,Chute,Elmhurst,Eversley,Glenlogie,Mount Cole,Mount Lonarch and Raglan. Authorities advise it remains unsafe to return home.

CFA deputy chief Garry Cook said the conditions were all there on Wednesday to heighten the bushfire risk.

“The air mass is really dry,it’s got a strong northerly wind pulling all that hot[and] dry air down over Victoria,and then a blustery southwesterly change will come through late in the evening,” Cook said.

“Our job now is to – where we can – prevent anything from starting,and that’s[also] the community’s job.”

Crews were working day and night to consolidate a firebreak around the massive blaze but the steep landscape made it difficult to tackle,Cook said.

The CFA did not expect to have the blaze under control by Wednesday,the deputy chief said.

Firefighters have worked hard to deepen the control line on the southern side of the Bayindeen fire in recent days,and NSW crews were to arrive on Tuesday to help.

“We will have a significant amount of resources deployed,both aircraft and ground crews,for Wednesday to there,” Cook said,adding that they were also preparing for new fires to break out.

“There is a potential ... for some lightning later in the afternoon or the evening as the change progresses across the state.

“We’re hoping that doesn’t occur,but if it does,it’s likely to be dry lightning.”

Crews were tracking weather conditions hourly with the Bureau of Meteorology,Cook said.

He warned Victorians against risking starting fires while the danger was so high,including by operating machinery in vegetation,mowing,welding or grinding.

“Our primary objective is to make sure we don’t lose any lives,and the community so far ... have been heeding the warnings,” Cook said. “We’ve got another really tough day to go,and we just ask the community to continue to do their bit.”

With Broede Carmody,Lachlan Abbott and AAP