Fire Safety officers and Tauranga detectives are unable to pinpoint the cause of a blaze that charred the inside of a Mount Maunganui unit this week.

Fire broke out in the living room of the brick single storey unit about 3.15pm Monday - just minutes after the resident and her child left the home.

The inside of the Mount Maunganui unit that caught fire on Monday.

Fire Risk Management Officer Jon Rewi says the fire is being treated as suspicious as a precaution and the case has been handed to police for further investigations.

'I have not been able to find a cause and there are certain elements that have led me down that path.”

Samples have been taken from the scene of the fire and will be sent off to be analysed.

Tauranga Police Detective Senior Sergeant Greg Turner says the fire is not believed to be arson, but further investigations are required.

'We have worked with fire safety and it remains unexplained. We are having samples sent for forensics, including testing of an electrical appliance. It's unexplained rather than arson at this stage.”

The woman living at the home had left the property around 3pm and before travelling far realised she had forgotten her son's sports uniform, so returned to collect it.

By this time a quick-thinking neighbour, who spotted flames coming from the floor level of the home from across Epsom Reserve, had run over and grabbed a garden hose to stop the fire spreading from the living room to other rooms.

Mount Maunganui firefighters received the call at 3.25pm and were able to quickly extinguish the fire.

Despite containing the blaze, Jon says there is extensive smoke and heat damage throughout.

'The house was severely damaged with smoke and heat. People need to be aware that even a small fire like that can devastate the house – the smoke and heat layer went through the house to about a metre off the floor.

'If anybody was in that house at the time, they would have been dead.”

There were two smoke alarms in the home, but Jon says neither was actively working.

'The occupant told me that she had taken the battery out of one of the smoke alarms to use in a toy.”

Jon urges people to remember that smoke alarms do save lives, and it is imperative they are working.

'If it had happened at night and they were asleep there is a very high chance they may not have woken up, that heat layer usually generates about 500 degrees Celsius.”

All the doors in the home were also open, fuelling the fire, allowing smoke and heat to travel throughout the home.

Remains of an air conditioning unit were also located near the seat of the fire, but Jon doubts this is the initial cause.

'We are going through the causes and we can't discount it.”