Authorities had been called to the home on Cornelia St at about 9.45pm on Wednesday, following reports of a fire. The blaze reached the windows of the home before five fire trucks and 20 firefighters arrived, Fire and Rescue NSW officials said. Fire and Rescue NSW Commissioner Jeremy Fewtrell attended the scene on Thursday morning and promised an extensive investigation into the fire's cause. "We remind people the importance of having working smoke alarms, and that's a working smoke alarm that you've actually pressed the button and you've heard the noise." Police will work with the extended family to understand what led to the tragedy, Superintendent Sheridan Waldau said.