A woman on fire was seen running out of a house after an explosion at a South Auckland address.
Four people have been seriously burnt in the blast, which was in the upstairs bedroom of a unit in Otara.
Northern Fire Service spokesman Jaron Phillips said neighbours saw a person running from the house on fire.
Two crews are at the scene, attacking the blaze.
Crews were called to the Lappington Rd address at 2.42 this afternoon.
Tamea Vaisima lives on Lappington Rd, and told the Herald she didn't hear the explosion but her grandchildren saw emergency services at the address on their way home from school.
"I can see a lot of fire trucks around and police, it's pretty scary."
A local resident described seeing a woman burning "from the hips down" and another person badly burned at the address.
The blaze is understood to have started in the upstairs bedroom.
Lappington Rd has been closed by police and a Specialist Fire Investigator is now on scene.
A St John spokesman confirmed four patients were being transported by ambulance to Middlemore Hospital.
The fire is not thought to be suspicious.
The Fire Service said the fire was over a small area, but materials stuck to skin and that's what caused the injuries.
One of the occupants said they went upstairs and lit a cigarette. A lighter was found in an upstairs bedroom.
There were five people in the building when emergency services arrived.
The Fire Service said there is nothing to suggest drugs were being made at the property.
Police said they are speaking to four people who are assisting with their inquiries.
They are seeking the fifth person who was in the house and other witnesses.
Police said they don't know the identity of the fifth person in the house.
Police said they're dealing with young people who are injured, in their mid-teens.
Police Inspector Kerry Watson said emergency services were at the scene of the fire in the bedroom of a house in Otara.
Police, fire and ambulance are all at the scene. Four people are being treated for injuries and are being taken to Middlemore Hospital.
One person has critical injuries, while another is moderately injured. Two other people are being treated for smoke inhalation.
A witness posted on Facebook they were on Lappington Road when they saw one female burnt from her hips down and another person who was also "really burnt". "Jesus be with the family on Lappington," they wrote.
Watson said there is no risk to nearby residents and the fire has been contained.
Cordons are in place at Lappington Rd while police and the Fire Service work to establish the cause of the fire.