Shortly after 5pm a second fast-burning fire grass began burning north of the initial blaze or Bungendore Road between Collector Road and Lumley Road in Tarago.

Three trucks on the scene and were able quickly control the fire which began nearby a property.

Firecrews were hard at work all afternoon battling the larger blaze. By 2pm had been downgraded to a "watch and act" alert, as crews set up containment lines around the fire.

Firefighting continued along Mt Fairy Rd, with a small pine forest near one home in smoke as fire trucks stood to defend the property.

Out west, past Lake George, smoke was climbing above the hills while the wind turbines stood still.

NSW Rural Fire Service captain Peter Bavington was overseeing one line, watching the smoke on the horizon west of Goulburn Road.

"Trying hard to get back to normality," Mr Bavington said. "There's basically no flame."

Most of the fire was embers and spot fires, while smoke was still visible on the hills between Tarago and Mount Fairy.

The main concern was the chance of embers picking up and lighting any grass east of Mr Bavington's position, and a small strand of bush where fire crews had pulled out earlier to allow water bombers to target it.

Mr Bavington had 30 trucks at his disposal along Goulburn Road plus ACT chainsaw crews, while locals were manning utes loaded with water tanks at the driveways to their properties.

NSW Rural Fire Service spokesman Paul Best said crews were "finding it difficult" to hold the blaze on an area that crossed east of Goulburn Road and reached to the west of Bungendore Road.

There was an extreme fire danger rating for the area and Mr Best warned that conditions could deteriorate quickly.

"The fire is behaving very erratically due to the weather so people should remain vigilant."

He said 135 firefighters from across the region, including seven aircraft, were battling the fire in 37-degree heat and winds that gusted between 50 and 80 kilometres an hour.

The fire had burnt through Taylors Creek Road, Bungendore Road and Mount Fairy Road.

Firefighters were seen battling the front along Goulburn Road, with helicopters swooping constantly over nearby farms to collect water from their dams.

This included one property off Hazeldell Road in Mount Fairy, which had been destroyed while builder Scott Williams overlooked the log cabin he had helped his boss renovate.

"It came roaring across the paddock in a matter of of minutes," Mr Williams said. He had watched as the fire approached.

He said the fast-moving grassfire had caught out one fire truck. The firefighters inside hunkered down until the flames went over them.

He and two others, who look after the property, had moved the cattle out but the sheep were mostly gone, some lying dead in the nearby paddocks with eyes open and fur burned off.

Nearby, Mulloon Creek farm had come close to being destroyed as fire circled the chicken sheds, but as the smoke cleared in the morning the owners saw they had only lost six of 20,000 hens.

Tarago Road and Goulburn Road remain closed to traffic and the Goulburn Queanbeyan Railway is also closed, with traffic being diverted to the Federal Highway, causing significant travel delays.

Mr Allen said the Rural Fire Service was investigating the destroyed property in Hazeldell Road area, as well as livestock loss.

"We have got our building impact assessment in the area to confirm that and determine what type of property it is," Mr Allen said.

"We are also looking at reports of two sheds and a couple of vehicles that have been damaged and livestock lost."

More than 30 units from the Southern Tablelands and Lake George zones, as well as ACT's Fire and Rescue and Royal Fire Service, were first called on Tuesday to join the fight.

ACT Emergency Services Commissioner Dominic Lane said two senior volunteer groups from ACT RFS remained on scene overnight on Tuesday.

Additional crews and two ACT fire bombing helicopters returned on Wednesday.

"We stand ready to provide further assistance to NSW if they need it," Mr Lane said.

ACT Fire and Rescue announced the first total fire ban for the year on Tuesday, with severe weather warnings expected to impact the blaze.

Total fire bans are also in place for Goulburn Mulwaree, Palerang, Queanbeyan, Upper Lachlan and Yass Valley.

Mr Allen said residents should enact a bushfire survival plan, which can be found at myfireplan.com.au.

"They should not only make the bushfire survival plan but discuss what they would do with family," Mr Allen said.

Authorities recommend residents download the Fires Near Me smartphone app and follow firefighters' advice if their property is under threat.

As 6.30pm on Wednesday 32 residents who had left or were evacuated from the area had registered their details with police. The register was opened on Wednesday morning as part of the emergency operations protocol.