Photo: The fires on the ridges to the south of Canberra, as seen from Mount Ainslie last night. (Supplied: Jacob Ross)
Canberrans who are potentially blocking routes to the bushfires to the city's south are "a disgrace", the ACT's emergency chief says.
The out-of-control fire, which began in Namadgi National Park on Monday afternoon, has been downgraded to advice level after spreading rapidly yesterday and threatening the village of Tharwa.
However, Emergency Services Agency (ESA) Commissioner Georgeina Whelan said conditions were likely to worsen later this week, when temperatures were predicted to soar.
She also blasted Canberrans who were hampering her agency's work by blocking roads in and out of fire area.
"Say no to disaster tourism — it's a disgrace," Ms Whelan said.
"I want to get firefighters in there, I want to get operational staff in there, I want to get police in there to protect our community."
She said the roads needed to be clear in case residents in southern ACT suburbs wanted to evacuate.
"We had reports last night, and visuals, of cars driving down into the south, and parking their car, to get a photo."
She said there were "plenty of photos of already on Instagram" and Facebook.
"So if you don't need to be near a fire, take my advice: stay home."
Helicopter 'engulfed in flames' in 12 seconds
Meanwhile, the military has provided more details about the incident that started the bushfire on Monday afternoon.
The Defence Department said yesterday that heat from the landing lights of one of its troop transport helicopters likely ignited the fire.
Twelve people were on-board the aircraft when it used the lights to land safely in thick smoke while on a reconnaissance mission.
Major-General Jake Elwood said today the event was "absolutely regretful".
"The helicopter came down to land and, within about 12 seconds, the aircraft was almost engulfed in flames," he said.
"If not for the actions of that crew, it would have been a very different outcome.
"And so the crew have done a wonderful job in saving everyone on-board that aircraft."
The army has suspended its use of the landing lights while it completes its investigation.
Fire erratic and likely to worsen
Weather conditions are expected to worsen later this week, when temperatures will likely reach well above 40 degrees Celcius in Canberra.
Ms Wheelan said fire activity had increased on the blaze's western side today, and it was spotting well ahead of the firefront.
More than 40 firefighting crews were on the ground and aircraft were carrying out water-bombing
However, there was no immediate threat to property in Canberra suburbs.
"We are expecting the unpredictable," she said.
"This fire, and fires nationally, have not behaved in the traditional manner, they are quite erratic … it is unprecedented."
She said the next four days would be challenging.
"We are going to have very high temperatures, we have massive amounts of fuel as a consequence of the drought and very, very dry weather," she said.
"We are in for a big four to five days ahead."
She urged the community to remain "alert but not alarmed" and to be prepared.
"On our worst fire day, I can't put a fire truck on every corner," she said.
"But on our worst fire day I can have Canberra as prepared as it can be to respond and keep safe."
Tharwa residents help extinguish spot fires
The fire is burning within 5 kilometres of Tharwa, which is covered in a thick layer of smoke.
The blaze came over Mount Tennent and spotted close to the village last night.
Residents were told to shelter but, by 10pm, the danger had subsided as conditions eased.
"Locals and bushfire units had to put out spot fires on the hill behind us and a few places around us," Tharwa Community Association president Kevin Jeffrey said.
He said local farmers and residents remained concerned.
"It's a concern that the western edge of the fire has proceeded further west than we were initially expecting and that means it will come out closer to Tidbinbilla," he said.
"The farming country up there is steeper and more forested … so it is a concern as it heats up."