A massive fire that destroyed a Christchurch pizza factory and forced residents to stay indoors due to smoke on Tuesday is not deemed to be suspicious.
Authorities confirmed the single-storey building is the Romano's pizza factory in Hillsborough. Fire crews were alerted about 1.15am.
Up to 11 fire crews made up of about 50 firefighters battled the blaze and a fire investigator was sent to the site.
Fire investigator Darren Aitken said the investigation was focusing on one part of the factory.
While a definite cause has not yet been determined, he said "we are not regarding it as suspicious".
The Canterbury District Health Board issued a public health notice due to the smoke from the fire.
A spokesperson said: "Air around this location is smoky and there is potential that people who are sensitive to smoke, such as those with heart or lung conditions, pregnant women, young children and the elderly, may experience symptoms including coughing, shortness of breath or eye, nose and throat irritation."
Medical Officer of Health Dr Ramon Pink said exposure to smoke can worsen pre-existing health conditions such as asthma and heart disease.
"People affected by the smoke should close windows and doors and reduce outdoor exercise. Plastic, including polystyrene is a significant contributor to this fire and the smoke is considered toxic."
Fire and Emergency NZ is continuing to get the fire under control. The Northeast wind is sending smoke in the direction of the Woolston industrial area, Ferrymead and Sumner, he said.
"Anyone experiencing health issues from the Romano's pizza factory fire in Hillsborough should contact their general practice team for advice, in the first instance," Dr Pink says.
No one appears to have been inside the building when the fire broke out and there are no reports of injuries.
Residents were urged to stay indoors as the blaze caused a lot of smoke that might be toxic, authorities say.
- Additional reporting Star News
Police are appealing for more information.