Police are treating a Newtown boarding house fire as a suspected murder after three people were killed and another is unaccounted for.
Residents woke to large flames engulfing the building opposite the Carlisle Castle Hotel in Newtown.
Several residents became trapped inside the property after part of the first floor collapsed in the blaze.
NSW Police Assistant Commissioner Peter Cotter said the fire was being treated as a murder and had been "maliciously lit".
"We are treating this as suspicious — it was an explosion, the flames took hold extremely quickly," he said.
"It would be fair to say some type of accelerant was used — we are treating this as a murder, we are treating this as a maliciously lit fire.
"The three people who we have found dead are men but we have been unable to identify them yet — we are working with other residents to identify them," he said
"It is clearly a place that is transient with people coming and going — so it is making confirmation of the identity of those who perished difficult to confirm."
Police said they were yet to talk to the owner of the property, but are urging him to come forward.
"We would like that gentleman to come forward as a priority — particularly to talk to us about who was inside," he said.
An 80-year-old man called Ronnie is believed to have jumped from the first floor to escape the inferno.
Unable to walk and covered in blood, locals had to carry him to safety until paramedics arrived.
He was taken in an ambulance to Royal North Shore Hospital, where he remains in a critical condition.
“Apparently he was on fire and we are only assuming that he jumped through his window because there was no other way out,” said Peter Bouwman, who lives in the boarding house.
“I have never seen that man that colour in my life. It was a mixture of grey and green.”
Two others were also taken to hospital for treatment for serious burns and smoke inhalation.
Five people managed to escape the blaze unscathed.
Ronnie was a regular at the Carlisle Castle Hotel, where he recently celebrated his 80th birthday.
“If Ronnie gets relocated, he is obviously not going to move back there if he pulls through – that will finish him,” said Burnie Godzik, who is a friend.
“He has got nowhere to go – he’s the sort of person that this is his community, this is his life.”
Questions have been raised over the safety of the boarding house after some residents complained of exposed electrical wires.
“Roofing problems, electrical problems, gas problems – it has been ongoing and the council is aware of this,” Mr Bouwman said.
Large wooden blocks are being used to stabilise the boarding house while investigators search for anyone trapped in the rubble.
Police are expected to interview the owner of the building, while the Arson Squad has been called in to investigate the cause of the fire.
Several neighbouring homes were evacuated as a precaution.
