The scene guard will remain in place overnight.
"We are not aware at this stage of any public safety risk, but we are still in the initial inquiry stages," a police spokeswoman said.
Neighbour Sam Afungia said he heard sirens and the police helicopter flying overhead some time before 8pm while he was working in his garage.
"It was flying all over and it was very noisy. I thought maybe something had happened in the neighbourhood."
But when he looked out across the road he saw "heaps of [police] cars - maybe six or more" outside a property near Bairds Rd.
A large number of police can now be seen walking around the property with flashlights, he said.
"There are police walking around with torches - they are everywhere. Looking at the house, the fence," he said.
He believes a family with intermediate to high-school-aged teenagers lives in the state house.
"Sometimes when I drive by I see the dad outside smoking."