Four children have died in a fire that tore through a house in south-west Melbourne.
Police said the fire started at the house on Mantello Drive in Werribee shortly after 1am on Sunday.
Firefighters said the home was well alight when the first crews arrived about 1:10am.
Video taken by neighbours showed a wall of flames billowing from the single-storey home.
Part of the roof collapsed during the fire and authorities later confirmed the house was deemed completely destroyed.
A man, a woman and their eight-year-old child were taken to hospital with smoke-related injuries after escaping the blaze.
The 10-year-old and three-year-old boys and six-year-old and one-year-old girls were found deceased inside the home.
Neighbour Baljeet Singh and his family were woken by the fire and rose to see the property engulfed.
"It was the whole house, like a bonfire," he said.
"The roof was collapsing, there were collapsing noises.
After making sure emergency services had been called, Mr Singh and his family left their house because they were worried it could catch alight.
He said he did not know the family but was used to seeing them around the street.
Other neighbours told the ABC the fire was so bright, they thought the sun had come up early, and that the fire seemed to take hold rapidly.
Another said they saw the father screaming about his children as the house burnt.
Richard Carlesso arrived home from an evening out after 12:30am on Sunday and said the street was quiet.
"In less than half an hour … we heard the emergency services," he said.
"We came out the front, saw the house was starting to burn, a lot of people yelling and screaming, panicking."
Mr Carlesso said it was "incredible to see a house go up that quick".
"How three people got out of it is amazing."
Neighbours and emergency services workers were visibly shaken by the tragedy.
"It's very sad that four kids have lost their lives, and two parents and a sibling have to live with that," Mr Carlesso said.
He said the family were quiet neighbours and the children were familiar faces on the street.
It took about 40 firefighters just under an hour to bring the fire under control.
One of them was Damien Milloy, a lieutenant at the Werribee brigade, who said the size of the fire and the collapsing roof made the home very difficult to access.
"The fire itself we have seen many times before," he said.
Firefighters were able to protect the neighbouring houses from catching alight.
One firefighter was assessed by paramedics for chest pain, Mr Milloy said.
"It is a terrible set of circumstances, and one that's very difficult for the members of the family, and our hearts go out to the family and what's occurred here," Detective Senior Sergeant Ashley Ryan said.
"But also very distressing for members of Victoria Police and the emergency services, given the circumstances."
The Victoria Police arson squad is now trying to piece together what caused the fire and where it started.
Police are unable to say whether it is being treated as suspicious at this stage. Investigators are speaking to the hospitalised family members.
Specialist fire investigators from the Country Fire Authority and Fire Rescue Victoria are working with arson squad detectives on the investigation.
Mr Clancy said the fire had extended well throughout the house by the time he arrived to assist the crews.
"Firefighters had a fairly arduous task to undertake the fire fight and were unable to conduct an internal attack due to the heat of the fire," he said.
Counselling is being provided to the emergency crews who were on the scene.
