The blaze which killed two people in South Dunedin started in the rear flat of the property, a fire investigator says.
Fire and Emergency said it got a call about a house well ablaze in Wesley Street at about 5.15am.
Two people have been confirmed dead in the fire Photo: RNZ / Tim Brown
It tore through a wooden villa which contained two flats.
A specialist fire investigator, Mark Bredenbeck, said damage to the property was limited to the rear flat, where firefighters discovered two bodies.
Mr Bredenbeck said the damage there was extensive and the other flat, which an elderly man escaped from, has water and smoke damage.
While it was clear the fire started in the rear flat, the cause of the blaze was unknown at present, he said.
Officers arriving at the house said they could see the glow of the fire in the night sky as they approached, and at least four engines fought the fire.
Neighbours said they heard large bangs and cracks as the windows were blown out by the flames.
Fire and Emergency New Zealand said two people are confirmed dead, and police are working to formally identify them.
Extensive cordons were in place around the house, with police guards in place, RNZ's reporter at the scene said.
He said police and ambulance personnel were also at the house.
Neighbour Shane Corsan said two people lived at the rear of the property, while an elderly man living at the front was taken away by ambulance.
Wesley Street resident Dylan Ryall said his stepmother helped the elderly man out.
He said the man cannot walk without assistance and lives alone at the property.
Two people live in the rear flat, but neighbours could not reach them as they were beaten back by the heat of the blaze.
Dunedin detectives are also investigating.