A woman and her two young children escaped through a bedroom window as their home was engulfed in flames.
Emergency services were called to the blaze on Wise St, Wainuiomata about 12.15am yesterday.
Detective Caroline Martin said a woman had called for help after she awoke to find the porch and wash-house area of the house ablaze.
Wainuiomata Volunteer Fire Brigade chief fire officer Dave Smith said it took six fire trucks to bring the fire under control.
''The guy across the road is in our brigade and heard the yelling and screaming and the fire siren [at the station].
''He pulled two young children and the mother out of the room round the back of the house.''
The family were lucky a closed lounge door slowed the spread of the fire to the bedrooms, Smith said.
Police investigating the fire have completed a scene examination and the cause of the fire remains undetermined.
Hutt Valley detective senior sergeant Mike Sears said the area near the house was ''constantly'' plagued by deliberately lit fires.
''We're not in a position to say it's [the Wise St fire is] arson, we've got quite a few enquiries and forensic investigations to do before we could point in the right direction."
Martin said the home sustained extensive damage as a result of the blaze.
"Thankfully no one was hurt. The situation could have been drastically different if the family had not managed to escape through a bedroom window."
Police appealed for anyone with information about the incident to call Hutt Valley police on (04) 560 2600 or Crimestoppers on 0800 555 111
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