A home in Braddon was "well alight" when firefighters arrived to the property early on Monday morning.
ACT Fire received a call at 5.15am on April 29 when concerned locals saw flames "issuing" from the Ijong Street home.
ACT Fire acting commander Adam Gresham said it took three trucks to put the fire out.
"When crews arrived there were flames through the roof and already structural collapse," he said.
"We just did a defensive attack, and put the fire out.
"The house was not lived in, apparently there were squatters in and out but there is no evidence of anyone in there at all."
The blaze is being controlled and ACT Emergency Services said they'll stay at the site until late into the morning.
Mr Gresham said the site will then be handed over to fire investigators and the Australian Federal Police.
No injuries have been reported.
The Canberra Times understands part of Ijong Street is closed, but one lane will reopen once fire crews leave.
The public is urged to avoid the area.
