At least one home has been destroyed and more are expected to be lost as firefighters face days of battling a massive blaze in western Victoria.

Tens of thousands of residents from communities near Ballarat were told to “leave immediately” as the bushfire, which began at Bayindeen, accelerated and ultimately ripped through more than 11,000 hectares as of Friday.

About 1000 firefighters, hundreds of trucks and almost 60 aircraft – including four large air tankers – have been battling the blaze, with investigators yet to determine the cause.

Country Fire Authority chief officer Jason Heffernan confirmed at least one home was destroyed but he expected more structures were already lost.

“I also expect there to be significant outbuildings, fence losses and (there are) likely to be stock losses as well,” he told reporters.

Impact assessment teams started to assess the scale of the fire’s destruction on Friday.

A wind change late on Thursday had the bushfire shift direction from southeasterly to northeasterly.

Crews were focused on the under-threat communities of Elmhurst, Amphitheatre and surrounds on Friday, and expected some milder conditions ahead of another potential “fire spike day” on Wednesday.

Winds reached about 69km/h on Friday morning but were expected to stay at about 30km/h for the remainder of the day.

“It will take some time to contain the fires – it will be a lot easier in the open grassland and farmland where we will use dozers and graders to create containment lines,” Heffernan said.

“In the bushland areas, that will be a little bit more complicated.

“I do anticipate we’ll have some solid containment leading into Wednesday.”

The CFA would work with other agencies to plan an ongoing operation for at least seven days, Heffernan said.

More than 25,000 homes were sent emergency alerts through voice or text messages on Thursday and about 5500 more went out on Friday morning.

Premier Jacinta Allan said it was a tough night for residents west of Ballarat.

Emergency Services Minister Jaclyn Symes warned the fight against the bushfire was not over.

“I can’t underestimate – this is a massive fire, it moved quickly, it grew fast, and that’s why we have more than 175 trucks (and) 1000 personnel (on site),” Symes told reporters.

Symes said the 175 trucks were in addition to local fire crews’ vehicles.

Relief centres were set up at Ararat, Maryborough and Wendouree – the latter, attracting 200 registrations.

Of those who registered, eight people stayed at the centre overnight and a further 50 slept outside in caravans and other accommodation, mostly because they had pets and vehicles, Heffernan said.

The very large bushfire forced the closure of the train line between Ballarat and Ararat, which authorities hoped to reopen by Saturday.

Other road closures were also in place on Friday.

Prisoners with health conditions that make them vulnerable to smoke have been taken away from Langi Kal Kal Prison, which is near the fire.

Emergency warnings, a watch and act and advice alerts remained in place on Friday for several communities north of Beaufort as the bushfire headed towards the Elmhurst and Amphitheatre region.

A high fire danger alert has also been issued for parts of central and south western NSW, in addition to the Greater Hunter region.

Hot conditions on Friday were likely to be focused on Northern and Eastern NSW, Bureau of Meteorology meteorologist Dean Narramore said.

The mercury was set to reach the mid to high 30s in Sydney before widespread thunderstorm activity and a cool change in the evening.

In WA, a heatwave warning is current for the Pilbara, North Interior, South Interior and Gascoyne regions.

A bushfire watch and act alert is in place for people travelling along the Eyre Highway near the Balladonia Roadhouse in parts of Balladonia and the Fraser Range in the Shire of Dundas.

– AAP