The blaze broke out at the Pavonia Street home about 5:30am, with authorities alerted by a triple-0 call.

Police say the fire is being treated as suspicious and forensic officers are expected to spend several days examining the scene.

Detective Acting Inspector Joe Zitny said on Tuesday afternoon police had not yet identified any of the victims.

He said they were seeking assistance from anybody who saw or heard "anything remarkable" in the 24 hours leading up to the fire.

"There was a set of circumstances that as we are investigating them there's been one or two signs that have indicated and aroused our suspicions and we're pursuing those lines of inquiry," he said.

"Any people that may have noticed anything or saw something remarkable, or something out of place, or something different, in the vicinity of Pavonia Street in Everton Hills … please make contact with Crime Stoppers."

Inspector Zitny said the house had been "significantly damaged", and as a result it had taken several hours for police to gain access.

"Our forensic people are scouring the crime scene as we speak," he said.

"It's anticipated it's going to be a number of days … to finalise what we describe as the crime scene of the house."

Asked about reports cars were seen speeding away from house after the fire started, Inspector Zitny said that was one of several lines of police inquiry.

"The crime scene is presenting a number of barriers to the authorities at present. We're slowly but surely working through those barriers and we'll certainly conduct the identification process as soon as we can," he said.

Earlier, Inspector Dan Bragg said neighbours reported hearing an explosion coming from the home.

"What we're advised is that it was quite a large explosion, quite significant, and the neighbour that heard that explosion immediately contacted police," he said.

"We also spoke to one neighbour who gave us advice that there was some yelling beforehand."

Neighbour Lindsay Ostrofski could see the fire from his verandah. ABC