Meanwhile, the Pialligo fire that threatened homes on Wednesday night has been upgraded to emergency level again and residents have been told it is too late to leave.

The ACT Emergency Services Agency said the fire started about 11am and was at watch and act level. Firefighters are at the scene, but it is burning out of control.

"People in Pialligo, Brindabella Business Park and surrounding areas could be affected by a bushfire in Kallaroo Road, Pialligo, conditions are changing and could get worse," it said in a statement.

There are reports of confusion in the area, with people trying to get out and unsure of where and whether to go.

Police said there were road closures in place at the Canberra Avenue and Hindmarsh Drive intersection. There were also road blocks on Canberra Avenue at the intersections of Norse Road, Tom Price Street, Gilmour Road and Kendall Avenue. Please avoid the area and follow directions.

The fire is travelling south easterly towards Pialligo Avenue.

No properties were under threat from this fire as of 11am. Authorities are using water bombing helicopters to attack the fire.

Kallaroo Road houses several gardening and landscaping stores, and orchards. There are reports that some staff are being evacuated from offices around the airport and of road closures in the area, but the ESA was urging people at Brindabella Business Park to stay where they were because they were safe.

An hour earlier, Michael had been watching the fire from a balcony on his Brindabella Park office with colleagues.

"As you say it's not something you see everyday so it's probably the worst day you could get a fire out," he said.

"I wouldn't like to be putting a fire out in today's conditions."

Michael was only 30 seconds into his conversation with The Canberra Times when he had to evacuate from the balcony.

All passenger flights in and out of Canberra airports have been halted because of the fire. The airport terminal has not been evacuated. Passengers have been advised to contact their airline for the latest situation.

The decision by the airport authorities was taken to so that passenger planes wouldn't interfere with the movements of fire-fighting aircraft. The fire is being attacked by a series of helicopters which are moving over the wider area.

The fire has started during a total fire ban. There is also a severe weather warning for the ACT and region, for damaging winds with peak gusts of up to 90km/h expected.

READ MORE:

It is understood the fire started at the old Duntroon dairy farm when the wind blew over a tree on to power lines.

Duntroon Dairy farm, in Pialligo, has been in Gary Brodrick's family since the Second World War.

What was once a 140-acre property has dwindled down to just over 10 acres and a bushfire on Thursday threatened what was left.

My Brodrick said the fire started when a tree branch fell off due to strong winds and hit a power pole that encroached on his neighbours property.

"It just took off in a matter of 10 to 15 minutes," he said.

"I was at my truck and then I just looked and there was a fire and it started taking off, I didn't know which way it was going.

"And the wind is really strong... it's a bastard of a day."

There were several crews fighting the fire on Mr Brodrick's property.

"They we're pretty quick to get here," he said.

Mr Brodrick had fielded many calls from friends and family concerned about him.

Also about 11am on Thursday, firefighters were also called to a tree alight in the middle of the road on the intersection of Bowes Street and Launceston Street in Phillip.

There was another tree fire in Monash about 11.30am.

More to come