Police said 11 people in total were taken to hospital with injuries from the scene.
Four children have been taken to hospital with burns and smoke inhalation. Three of the children were flown by air ambulance to the Royal Children’s Hospital in a serious condition – a male infant, a female infant and a primary school-aged boy.
A preschool-aged girl was in a serious but stable condition and was taken to the Northern Hospital.
An Ambulance Victoria spokesperson said on Sunday morning that three adults were in a serious condition following the fire, and had been taken to The Alfred hospital burns unit – two females in their 30s and a male in his 30s – while another adult who was serious but stable was taken to the Northern Hospital.
A CFA media spokesman said 16 tankers were called to the fire, and it took firefighters about two hours to bring the blaze under control.
“A single-storey structure was fully involved [with fire] on arrival,” he said. “The last crews left the scene at around 5am. Crews will attend later this morning to ensure no further hotspots on the structure.”
A Victoria Police spokesman said the exact circumstances surrounding the fire are yet to be determined.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au.