A NSW Ambulance spokesman said paramedics had so far transported five people to hospital - three to Mount Druitt Hospital and two to Hawkesbury District Health Service.
”The situation is currently still unfolding,” an ambulance spokesman said.
A gas company was on site on Saturday afternoon trying to isolate the mains after it was unable to cut off supply.
”There is no fire at present but the scene remains volatile and unstable,” Fire and Rescue NSW said.
The fire service had more than a dozen units at the location and was also using drones to assess the blast zone.
Firefighters urged the community to stay away from the scene, while NSW Police from the Mount Druitt area were also attending.
A NSW Police Force spokeswoman said an investigation into the circumstances surrounding the explosion had begun.