A Kaiapoi couple who returned from a day in Hanmer were shocked to discover their two- storey home in Akaroa St gutted by fire.
The pair returned mid- afternoon on Saturday to find it surrounded by fire crews, with a large area on the ground floor badly burnt.
Fire investigation officer Mark Thomas said the fire started under the stair well, but it was not considered suspicious.
"I'm pretty sure it was accidental, but I'm not sure what caused it yet."
Neighbours raised the alarm at about 1.40pm, and the blaze was well under way when the crews arrived.
Kaiapoi chief fire officer Paul Dellis said six crews worked for about two hours to bring the blaze under control.
There was significant smoke damage to the whole house, Mr Dellis said.
- (Live Matches)