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Five people have been hospitalised after an explosion at a block of units caused a major building collapse in Sydney's west.
Emergency crews were called to a home on Waikanda Crescent in Whalan after reports of an explosion around 12.50 pm.
Two women were rescued from the ruins of part of the building and a search and rescue operation is underway to determine if more people were trapped in the rubble.
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A woman in her 60s and a wheelchair-bound woman in her 70s were rescued from the collapsed building.
They were treated by paramedics at the scene.
A total of five people have been taken to hospital after the blast.
Three people were taken to Mt Druitt Hospital and two people were taken to the Hawkesbury Hospital.
Their conditions are not yet known.
The cause of the explosion has not yet been determined.
"The large blast blew out windows and damaged neighbouring townhouses in the multi-apartment complex," Fire and Rescue NSW said in a statement.
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The gas company that supplies the building was initially unable to cut off gas to the scene and is attempting to isolate the main supply.
Fire and Rescue NSW said there was no fire, but described the scene as "volatile and unstable".
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.
