Neighbours say screams were heard last night when a Christchurch home went up in flames.
An 8-month-old girl and a 10-year-old boy died after the fire, in the Vivian St, Burwood neighbourhood.
Two others in the home when the fire broke out were taken to hospital.
An unnamed neighbour said it was just "devastating".
"We heard screaming and then just all the flames, we tried to get the hose out to try and help."
A man, a woman and four children were in the house when the fire broke out.
Fire and Emergency southern fire shift manager Jill Higgison said emergency services received multiple calls about the fire just before 10.45pm.
Three fire crews arrived to find the single-storey home ablaze.
Another neighbour, whose house backs on to the damaged property, says he heard screams and cracking from flames at 10.30pm.
He quickly rushed out of bed and grabbed his garden hose, pointing it towards the burning house.
The neighbour said he heard screams from a male and children.
He also believes he saw fire crew carry a young boy out of the damaged house.
Higgison said some occupants were able to escape the blaze but two were unable to be rescued.
One fire crew remained at the scene overnight to monitor hot spots, and a fire investigator was due at the scene today.
A St John spokesman said two ambulances and two rapid response crews were called to the burning home.
Two people were treated at the scene and taken to Christchurch Hospital.
NZ Gift of Love and Strength a Christchurch-based charity is taking donations for the family which can be dropped of at Little Explores Preschool, a local preschool.
The 19-year-old disappeared without her wallet or mobile phone.