Whalan explosion: Grim development as search and rescue mission ramps up for woman trapped under rubble after explosion destroyed a townhouse

Rescuers have ramped up the desperate search for a woman feared to be stuck underneath a pile of rubble after a townhouse was destroyed in an explosion. 

The blast occurred on the second level of the property on Waikanda Crescent, in Whalan, in Sydney's west, with Fire and Rescue NSW (FRNSW) called just before 1pm on Saturday.

Police announced on Sunday that the search area is now a crime scene and officers have closed off the street. 

There has since been an increased police presence in the area as dozens of officers descended on the scene around 7.30am.    

Paramedics treated five people after they suffered injuries following the collapse of the building. 

Two women were rescued from the collapsed structure's rubble - a woman in her 60s and another woman in her 70s who uses a wheelchair.

Another 12 people from surrounding houses were evacuated.

More to come.