A man is in a critical condition in hospital with burns to 60 per cent of his body after a fire broke out in a block of six townhouses in Queanbeyan on Friday night.
One townhouse on Thuralilly Street has been completely destroyed by the fire while a second suffered significant damage to the roof and a third recorded only minor damage.
Firefighters were forced to knock down the walls of the worst-damaged townhouse, which had been left structurally unsound by the blaze.
A Fire and Rescue NSW commander at the scene said he believed the fire had been caused by a domestic accident involving petrol and a naked flame.
Six ACT fire and rescue crews along with two NSW fire units and two commanders attended the scene, following several Triple-0 calls to emergency services.
Ambulance crews also attended and took one man to Canberra Hospital with burns to 60 per cent of his body. He was in a critical condition at 9.30pm.
Fire crews evacuated 12 residents from nearby townhouses, several of whom were expected to be allowed back into their buildings about 9pm. No other residents were injured.
Residents from the two adjoining townhouses were not expected to be allowed to return overnight as their buildings were still structurally unsound.
Fire and Rescue NSW zone commander Ray Buchanan said arriving crews found the townhouse well alight and were unable to enter the property.
He said it took fire crews from the ACT and NSW about 40 minutes to bring the blaze under control.
"The fire extensions to the two adjoining townhouses took around 20 minutes to get crews in there and to stop the fire extension,'' he said. ''And it was extending through the roof space."
Mr Buchanan said crews initially did not know anyone had been injured in the fire, as the occupant had sought help from a neighbour who performed first-aid.
A neighbour who lives in an adjoining townhouse said he was at home when he heard yelling.
"I went outside and looked into the neighbour's garage and I saw it was on fire. But there wasn't much I could do," he said.
Queanbeyan resident Susan Dalituicama, whose carport backs onto the townhouses where the fire occurred, said she heard yelling, followed by some explosions.
"I came outside and had a look and there were just flames and smoke everywhere," she said.