The house fire in Oamaru damaged a second and third property before it was brought under control by the firefighters who swarmed to the scene.
Emergency service rushed the fire on Reed St, which runs parallel to State Highway 1.
Police at the scene said a 17-year-old Oamaru youth was understood to have escaped the house just before fire crews arrived.
A St John spokesman said the teenager was taken to hospital with minor to moderate injuries.
He was taken to Oamaru Hospital in an ambulance and police described his condition as serious.Police said the fire, which extensively damaged the property, broke windows and melted guttering on two neighbouring properties.
The fire was being treated as suspicious and CIB and a fire investigator from Dunedin had been called to the scene.
A Fire and Emergency New Zealand (Fenz) spokesman said two fire engines from Oamaru were in attendance, and another three were called in from neighbouring towns.
Within minutes Fenz established that everybody was clear of the house and attempted to stop it spreading to the neighbouring properties, he said.
"It did spread to a neighbouring property but it has all now been contained and extinguished and the crews are dampening down."The damage to the second property was believed to be minor. The damage to the first property was extensive, he said.
Two police cars also attended the blaze.
Smoke was billowing from the house, which had been significantly damaged.
At least 15 firefighters had battled the fire, some wearing breathing apparatus.
A baby stroller and three children's bicycles were on the lawn.
About 100 people had looked on at the house fire, with the smoke from it visible from the centre of town.
Emergency services had blocked off part of the street.
- Otago Daily Times, NZME
