Rural firefighters have spent much of the night battling a fast-moving and erratic fire that has been threatening two communities on Queensland's Darling Downs.

Key points: Authorities are still unsure of the extent of the fire's impact at Forest Ridge and Cypress Gardens

Authorities are still unsure of the extent of the fire's impact at Forest Ridge and Cypress Gardens An evacuation centre is open at Millmerran Showgrounds

An evacuation centre is open at Millmerran Showgrounds Part of the Gore Highway has been closed

Residents of Forest Ridge were told just before 7:00pm to leave immediately. Earlier on Wednesday evening they had been told to bunker down as it was too dangerous to evacuate on the roads.

People in Cypress Gardens, on the other side of the Gore Highway, have also been told to leave immediately.

"Conditions are now very dangerous and firefighters may soon be unable to prevent the fire advancing," locals were advised on Wednesday evening.

"The fire may pose a threat to all lives directly in its path."

By 9:00pm, authorities warned conditions in the area were getting worse. The fire was at a Watch and Act level.

A Queensland Fire and Emergency Services (QFES) warning early on Thursday morning said fire had affected a number of roads in the area and the impact could be significant in some places.

But QFES said it could not yet access areas affected to determine whether properties had been lost.

"Power, water and mobile phone service may be lost," the QFES warning said.

QFES Acting Deputy Commissioner John Bolger said there were unconfirmed reports that two structures have been lost in the Millmerran fire, though it is unknown if these are sheds or homes.

QFES said the Gore Highway is closed between Cypress Gardens and the BP at Captains Mountain.

It is advising residents to evacuate towards Millmerran but that those who have already left the area should not return as it is not safe to do so.

An aerial of the Millmerran fire captures its size as it burns near Cypress Gardens and Forest Ridge. ( Supplied: Queensland Fire and Emergency Servicse )

QFES state coordinator Superintendent James Haig said on Wednesday night there were a large number of homes in the areas, and many adjoined bushland.

He said there had been early reports of property damage, which would be followed up when it was safe to do so.

"Through the night we're expecting that the humidity will not go up as it normally does," he said.

"So unfortunately the very dry air that we have over southern Queensland and particularly this area is cause for us to have concern.

"We don't think it'll settle down too much through the night.

"We'll be working on this fire all night and I expect we'll be working on it tomorrow as well, when conditions are expected to worsen, and going into the next few days it will be very hot and we'll also have some continuing dry air and a bit of an increase in winds."

The Millmerran fire approaches Douglas Grist's house. ( Supplied: Douglas Grist )

Douglas Grist from Cypress Gardens, Millmerran, left as the fire raged just a kilometre away.

"It looks like it [the house] could be lost, but I escaped with my life and the dogs," he said.

The Gore Highway has been closed between BP Captains Mountain and Cypress Gardens.

Toowoomba mayor Paul Antonio said an evacuation centre was initially opened at the Millmerran Community Cultural Centre, though this has since closed and a centre opened at Millmerran Showgrounds.

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"There are many people who have evacuated," Councillor Antonio said.

"We as a council have got the Millmerran Aerodrome going full bore, with the planes dropping water, we've got the evacuation centre in town and we'll do whatever we can."

'This is all new'

Rural Fire Service (RFS) state coordinator Wayne Waltisbuhl said they were dealing with an unprecedented fire threat and he expected it to continue through to February due to a lack of rainfall.

"The sort of environment that we're in now, no-one has seen before," he said.

"This is all new, the fire behaviour is all new, as far as resourcing we've never been at a point when we've run out of our own resourcing but we've had to start to tap into some international support that's coming in.

"What that means is that we are in an elevated fire danger all the time and then we get these spikes in the weather coming through — similar to the one we'll have for the next three days."