The fire is burning 4.6 kilometres west of the ACT border. It is about 35.5 kilometres from Canberra suburbs and 32 kilometres from the nearest remote property.

On Saturday evening, the Mary's Hill fire was 2125 hectares in size.

"Tireless efforts of ACT fire crews today with favourable weather conditions have reduced fire activity," an ACT Emergency Services Agency spokeswoman said on Saturday.

"ACT firefighters have also been driving the perimeter of Mary's Road to blackout and extinguish accessible hot spots. This work helped strengthen containment lines on all edges of the fire."

She said the Firebird 100 helicopter was able to conduct a reconnaissance flight to identify hot spots in the area. The information collected, along with footage taken by the crew, was used to task and brief crews working on the fireground.

The Firebird 100 helicopter is equipped with six GPS devices plus ultra-sophisticated systems of cameras and lasers that can identify the exact position of a fire, down to a single tree in the deepest bush.

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It can relay that information live back to screens in control centres, giving instantaneous maps showing fires in relation to already burnt-out areas devoid of fuel and potential new fire areas.

The aircraft has been hired by the ACT government's Emergency Services Agency for the bushfire season and will remain in Australia for as long as deemed necessary.

Meanwhile, conditions on the Dunns Road and Adaminaby Complex fires remain unchanged.

The Adaminaby Complex fire is "being controlled" and had burnt more than 90,000 hectares. It is 2.5 kilometres south west from the ACT border and 48 kilometres from Canberra suburbs.

The Dunns Road fire is "out of control" and is 18 kilometres from the ACT border. It has burnt more 330,000 hectares.

A state of alert is still in place for the ACT, and people need to be prepared with a Bushfire Survival Plan.