Authorities issued an emergency warning for an uncontrolled bushfire which threatening lives and homes in Bullsbrook, northeast of Perth on Thursday afternoon. Meanwhile, a “watch and act” alert was issued for a bush blaze near St Marys on Tasmania’s east coast where residents were being urged to enact bushfire plans.

It came as heatwave conditions began to hit large swathes of Australia’s eastern and southern coasts, bringing high fire danger to the bushfire-ravaged states of New South Wales, Victoria and South Australia.

While both fires in Perth and Tasmania were downgraded on Thursday evening, the Bullsbrook fire northeast of Perth remains out of control despite conditions easing slightly. The blaze is now at “watch and act” level, the Department of Fire and Emergency Services says.

The bushfire about 1.5km west of the St Marys township in Tasmania was brought under control on Thursday evening but severe fire danger will persist on the east coast, southeast and central regions on Friday.

As dozens of fires continued to burn across the country, the Bureau of Meteorology forecast a top of 39C in Melbourne on Thursday, while people in Adelaide (42C) and Canberra (37C) were also set to swelter.

The NSW government also announced an inquiry into the unprecedented bushfire crisis, which the premier, Gladys Berejiklian, pledged would “leave no stone unturned”.

Three firefighters were injured, while another has escaped unharmed, after a tree fell on to their truck in the Australian Capital Territory.

The crew were working to slow the spread of the 15,000-hectare Orroral Valley fire on Wednesday night when the tree crashed on to the tanker.

Three of them suffered non-life threatening injuries. All four crew members were taken by ambulance to the Canberra hospital for assessment.

Authorities in Victoria are continuing to open roads in fire-affected communities that had been isolated in the aftermath of devastating fires at the start of the month.

After confirming about 250 people had been able to return to Mallacoota, the Victorian emergency management commissioner, Andrew Crisp, warned of the weather ahead.

“Thursday will be warm, but Friday is a significant day for us with elevated fire conditions,” he said. “There’ll be storms that come through with the potential for dry lightning, so again it’s a challenging day for us.”

Max temperature forecast for Friday. Severe heatwave conditions developing this week, with very hot and humid days and nights to come before a change moves across #Victoria on Saturday. Check your forecast here: https://t.co/x7fOGUJqJs #VicWeather pic.twitter.com/wHLaoC8JUN — Bureau of Meteorology, Victoria (@BOM_Vic) January 28, 2020

In Canberra, where a massive bushfire south-west of the city came dangerously close to homes, authorities used improved conditions on Wednesday to prepare for what was forecast to be four days of sustained dry heat. The temperature was expected to hit 42C by Saturday, before a storm front comes through the city on Sunday.

The ACT’s emergency services commissioner, Georgeina Whelan, said authorities hoped backburning operations would slow the spread of the 10,000ha Orroral Valley fire.

Smoke from the blaze, which was described as most serious the capital has faced since the deadly 2003 bushfires, was expected to linger over the capital on Thursday morning.

The fire is believed to have been started by a defence helicopter’s landing light after it landed in Namadgi national park while on a reconnaissance mission.

The ACT’s Emergency Services Agency said a southerly wind change would push smoke from the blaze into the city centre.

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There was a “very high” fire danger rating in place for the ACT on Thursday, with temperatures forecast to reach as high as 38C.

Meanwhile, the NSW Rural Fire Service said very high and severe fire danger was forecast for parts of state over the coming days, particularly in the south-east.

Sydneysiders will be spared the worst of the heatwave, with a top of 29C on Thursday, steadily rising to 34C on Saturday. But across the fire-ravaged south coast, the bureau of forecast a top of 43C in Bega and 39C in Bermagui.

In South Australia, authorities have declared severe bushfire conditions in six districts, with a total fire ban in place on Thursday for lower Eyre Peninsula, the mid-north, the Mount Lofty Ranges, Yorke Peninsula, the lower south-east and on Kangaroo Island.

On Kangaroo Island, which has been devastated by fire, earthmoving equipment, water tankers and extra fire crews have been sent to strategic locations amid fears that hot spots across the existing fire ground could flare.

Severe Fire Danger across southern & central parts of South Australia Thursday, including Kangaroo Island & the Mount Lofty Ranges. Very hot and dry with moderate to fresh northerly winds. Stay up to date with @CFSAlerts and check weather forecasts here: https://t.co/Fk3BjohrwO pic.twitter.com/rAI3bIWKt1 — Bureau of Meteorology, South Australia (@BOM_SA) January 29, 2020

The blaze – which has burnt through more than 210,000ha – is officially contained but the Country Fire Service has said crews were still finding hotspots in various areas including Blue Gum Hill, Cygnet River and Vivonne Bay.

While the mercury was expected 42C on Thursday in Adelaide, it was predicted to soar beyond that in some regional centres, with Cummins, on Eyre Peninsula, among the hottest with a forecast high of 46C.

But the heat and high-risk conditions will be relatively short-lived, with storms moving across the state on Friday before heavier rain at the weekend.

with Australian Associated Press