"Any decision to repair or replace the property will be made in due course, once the extent of the damage is known."
Smoke billows from the burning house. Photo / Chris Wells Massive flames can be seen engulfing the property with black smoke billowing across the suburb of Long Bay and surrounding suburbs.
A Fire Service spokeswoman said they are considering it suspicious, but they did not know what caused it.
She said the house was "well ablaze", and six fire trucks are being sent out to combat it.
Fran Lietz, 13, was at home when she saw smoke.
"We saw some people walking over toward it. We called 111 and then walked down. There were a lot of people there.
The fire broke out at a house in Long Bay. Photo / James Dixon "We could see flames through the fence and the trees. I thought it was a barbecue on fire. "It was really hot, everyone was sweating."
Neighbour Sally Tasker said she could see smoke billowing from her house, and she went down with husband Mark to see what was happening.
The house is understood to be a temporary ranger's house. Photo / Devon Venter "The house has gone up in flames. It's pretty damn awful, the house must be burnt to a cinder."
At 5.40pm she said she could still see smoke, and that the fire was "not getting marginally better".
Six fire trucks have been sent out to combat the fire. Photo / Supplied Another neighbour, Margaret Brill, said the house looked like it was "completely gutted".
Another neighbour said the fire "caused a bit of chaos with people trying to leave the park".
Emergency services attend the scene. Photo / Alexandra Pronk Mike Hall said he saw smoke coming from Long Bay Reserve from his house on East Coast Rd.
"I was taking my washing out, and we're a bit higher up and I saw smoke coming from the reserve down there."
At 6pm, he said the smoke was "definitely dying now".
Traffic backs up near the fire. Photo / Rachelle Luxford Hans Pronk said the fire was coming from within the reserve.
"I was stuck in traffic so I got out of the car to have a look at what was going on, and I could see smoke and flames.
"It was the first house in the reserve, just past the bridge."
He said access to the park had been shut off but it was now reopened.
Mr Pronk said emergency services "looked like they had things under control".
Smoke seen from the house fire. Photo / Michael Hall Flames can be seen through the trees. Photo / James Dixon