A search is underway to find a person who is believed to be trapped underneath the rubble of a partially collapsed townhouse after an explosion occurred in Sydney's west.
Emergency crews were called to the home on Waikanda Crescent in Whalan, which collapsed after an explosion about 12.50pm.
"There is still one person believed to be under the rubble," Fire and Rescue NSW Superintendent Ross Genders said.
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"At this time, all we know is they're alive," Genders said.
"We have heard taps and noises, and those are generalised as being an indicator that they're alive."
Five people have been taken to hospital with minor injuries, including a woman in her 60s and a wheelchair-bound woman in her 70s.
The five people are in stable conditions.
Three were taken to Blacktown Mt Druitt Hospital and two were taken to the Hawkesbury District Health Service.
Rescuers are focusing their search towards the back side of the building, where the most rubble has collapsed.
Rescuers are continuing the process of carefully removing the rubble piece-by-piece.
The missing person was believed to be on the second level of the building when the floor collapsed in the blast.
Intensive care paramedics remain on the scene.
"The large blast blew out windows and damaged neighbouring townhouses in the multi-apartment complex," Fire and Rescue NSW said in a statement.
Police have said that it could take days to determine the cause of the explosion.
"There was a light, a bright light, then boom, my kitchen window blew out first, then the ceiling collapsed", nearby resident Walter told 9News.
"There's glass all over my verandah, two of my bedroom windows were smashed out, and my lounge room was smashed as well," nearby resident Leanne Ansell said.
The gas supply to the area has been cut off.
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Fire and Rescue NSW said the danger had been isolated to the area of the collapse.
More than a dozen Fire and Rescue units were deployed including HAZMAT and aerial drone units.
Members of the public have been urged to avoid the scene, and local traffic diversions are in place.