Police are treating the scene of a "confronting" house explosion in Sydney as a rescue operation as they continue searching for a woman feared to be in the rubble.
Emergency services were called to Waikanda Crescent in Whalan, near Mount Druitt, just before 1pm on Saturday after residents in surrounding streets heard a loud explosion.
Two women — a woman in her 60s and a woman in her 70s who uses a wheelchair — were rescued from the collapsed townhouse.
They were among five people who sustained minor injuries and were taken to hospitals in St George and Hawkesbury but have since been released.
The block of townhouses is owned by the state government and is used as residential housing for seniors.
Sarah Dawson lived in one of the townhouses which was severely damaged in the blast and returned to the scene on Sunday.
She was not at home at the time of the explosion.
"I'm sad, I'm shocked," Ms Dawson said.
"I can do nothing. My feeling is so sad."
Emergency services personnel have been working overnight to search for the woman they believe could still be alive.
Rescue efforts have been hampered by a fire still burning underneath the house and heavy rain overnight.
"This is a very confronting scene for all emergency personnel working in there at the moment," NSW Police Superintendent Trent King said
It is not known what caused the blast, but NSW deputy premier Prue Car said she was "deeply concerned" to learn gas was allegedly smelled by community members in the days leading up to the explosion.
In a statement this afternoon, minister for housing Rose Jackson described yesterday's events as "devastating", confirming she has ordered an investigation.
"I am deeply concerned to hear of accounts from residents who reportedly raised the issue of the smell of gas within the last 12 months," Ms Jackson said.
"I have instructed Homes New South Wales to urgently investigate this matter. The Department are currently checking maintenance logs for any history of this.
"I am monitoring this active situation closely as it continues to unfold."
She said her staff were at the scene yesterday assisting with the investigation.
'Well within window' of survival
NSW Search and Rescue Commissioner Jeremy Fewtrell said there had been "total destruction" of the building but said it was still "well within the window for someone to survive".
"In 1997 we had the Thredbo landslide, it was in the winter time, and it was almost a week before Stuart Diver was rescued," he said.
"It is still within a window of survivability and hence the focus of effort [is] to really explore the building as thoroughly as we can."
He said there had been no further tapping noises recorded after they were initially heard on Saturday.
"Some of those reports of tapping were probably a little bit unconfirmed yesterday, but it's a key part of the operational process to be tuned in for noises."
Emergency services are using specialist listening equipment to monitor for sounds.
'I don't feel safe'
Neighbours on Waikanda Crescent said they could smell gas for up to a year prior to the explosion.
Tan Sen lived with his family on the same street as the collapsed town house and was anxious for answers.
"I'm really worried…it could be gas or it could be something else. It needs to be properly investigated," Mr Sen said.
Tenants whose homes were damaged were being offered temporary accommodation and financial assistance, including vouchers for clothing and furniture. Counselling is also available.
Gail Matycz was among the residents moving to alternative accommodation. Her house was two doors down from the blast site.
"I'm not sleeping in my house tonight. I don't feel safe, not at all," Ms Matycz said.
"There must be damage underneath because there's all cracks and everything."
Commissioner Fewtrell would not speculate on what caused the explosion but confirmed there had been a gas leak at the site after the explosion which impacted the recue.
"The focus for the foreseeable future is going to be on the rescue operation, but obviously once that is concluded a key part of the investigation will be looking at the cause," Commissioner Fewtrell said.
Specialist rescue teams on scene
Police, Fire and Rescue and ambulance crews are on the scene and working in a "chain" to remove debris.
"We have had human chains of firefighters working throughout the night in the pouring rain," Commissioner Fewtrell said.
Engineers and sniffer dogs have also been assisting.
"Last night we had a detection dog run over the scene… unfortunately there was no indications, but all stops are being pulled out and we are doing everything we can," Commissioner Fewtrell said.
Commissioner Fewtrell said the search and rescue teams working on the site were highly experienced and were often deployed internationally.
"We've had a number of deployments, most recently to Türkiye last year," he said.
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