A fire south of Canberra Airport has been downgraded to advice level, after threatening lives and properties on Wednesday afternoon.

Key points: The fire is burning near Pialligo Redwood Forest in an easterly direction

The fire is burning near Pialligo Redwood Forest in an easterly direction People in Oaks Estate, Beard and West Queanbeyan were told Wednesday it was too late to leave

People in Oaks Estate, Beard and West Queanbeyan were told Wednesday it was too late to leave The fire burned more than 140 hectares, but is being controlled

Authorities are warning residents of Canberra and Queanbeyan to remain vigilant and listen to advice ahead of Thursday, when a total fire ban will be in place for the region.

At 5:20pm on Wednesday an emergency warning was issued for the fire, burning at Pialligo Redwood Forest, in an easterly direction on the border between the ACT and Queanbeyan.

The fire came within 600 metres of homes in the Oaks Estate area, and burned around 147 hectares.

"It moved very quickly into open country and fire crews very quickly got on top of this," ACT Fire and Rescue Chief Officer Mark Brown said.

"[They] prevented a bad fire impacting on residential areas in Queanbeyan and Oaks Estate."

The fire's status was downgraded to watch and act level shortly after 6:00pm, and again to advice level at 7:15pm once it was brought under control.

Fire crews remained on scene overnight patrolling the fire, protecting property and monitoring conditions.

Helicopters water bombed the fire and provided aerial surveillance. ( ABC News: Ian Cutmore )

On Wednesday night, Pialligo Avenue remained closed from Scherger Drive to Oaks Estate Road, and the Queanbeyan Railway Line was closed.

People from Oaks Estate and Beard, in the ACT, and Queanbeyan West, in NSW, had earlier been told it was too late to leave.

Video shot at a concrete recycling business in the fire's path showed the fire burning at the edge of the worksite.

The fire is burning just south of Canberra Airport. ( Facebook: Anthony Hayman )

ACT Emergency Services Commissioner Georgeina Whelan said the cause of the fire was not yet clear.

One property was actively protected by firefighters.

"The fire actually travelled to within 600 metres of the Oaks Estate Road," she said.

"The fire was burning on both sides of the Molonglo River."

Thirty-seven ground crews are fighting the fire and six aircraft. ( ABC News: Tom Lowrey )

Chief Officer Brown said they were investigating the cause of the fire in collaboration with the police.

He said there was a "good chance" it was started by an individual, possibly by accident.

"It's very close to the road-way there, so a good chance," he said.

The fire burns near Beard, an outer suburb of Canberra. ( Supplied: Rebecca Legge )

He praised the efforts of firefighters who responded to multiple emergency calls for help.

"We're still actively patrolling this fire but there is no risk to residents in those areas, so it was a great save by all services working together," he said.

"We've got a total fire ban in the ACT tomorrow as well as surrounding areas in New South Wales and a fire like this on a day like tomorrow will be even harder to control."

Six helicopters were used to water-bomb the fire while a special intelligence helicopter was used to send information back to the incident management team, he said.

The fire sent up smoke that could be seen for kilometres. ( Supplied: Alison Drower )

Commissioner Whelan advised residents to continue to listen to advice as firefighters worked to control the blaze.

"What we would ask individuals to do is remain alert," she said.

"If they feel uncomfortable and they don't feel safe in their homes then we would recommend that they do relocate into the Queanbeyan area."

West Queanbeyan resident Jacinta said she was sitting on her back verandah, overlooking the suburb of Beard, when the fire flared.

"We saw this big plume of smoke and there we saw a lot of flames," she said.

"We've seen a lot of traffic as well, people trying to get out of Queanbeyan I think, but a lot of fire trucks as well."

Loading

She praised the efforts of firefighters, including the use of water bombing aircraft.

"I think we'd be in a lot more danger if it wasn't for them," she said.

"They were on it pretty much straight away … I've never seen anything like it to be honest."

Strong winds are forecasted to impact the territory overnight ahead of the high fire danger day on Thursday.

Canberra Airport said flights had not been affected, but that those planning on flying should allow extra time for travel.