A BLAZE which gutted a Christchurch home last week started accidentally – but the scale of the damage means an exact cause can't be determined, firefighters say.

As reported, the detached house in Oak Avenue was devastated in the fire, which spread to neighbouring properties in Chestnut Avenue.

At the height of the incident on Wednesday night, some 70 firefighters were called in to tackle the fire. No one was injured.

A young family were due to move into the house at the end of July.

Fire crews quickly ascertained that the blaze wasn't deliberate. However, it has not yet been possible to find a reason for the fire due to the extent of the damage.

The matter is now in the hands of insurers.

BCP Council provided emergency accommodation for one household. The residents of two other houses were given help to find accommodation in the area.