A FIRE which raged for more than eight hours at a Homebase store in Liskeard was accidental, the firm has said.
Dozens of firefighters battled the blaze, which began just after midnight, on Saturday, when the fire alarm began sounding at the store at the Bubble Retail Park on Plymouth Road.
No one was injured but around a third of the stock was damaged, Cornwall Fire and Rescue Service has said.
The company said on Sunday fire investigators had confirmed they do not believe the fire was started intentionally.
Spokesman Adam Manning said: "We now know that the cause was accidental – we are just relieved no one was hurt.
"The fire was extinguished by 7am. I can't say how much damage has been done nor how many staff will be affected.
"For health and safety reasons we will not be trading until we can assess the extent of the damage."
A fire crew from Liskeard arrived first on the scene after reports of fire within the Homebase unit.
Other engines attended, after smoke began billowing from the eaves, followed by crews from Callington, Looe, Lostwithiel, Saltash, Bodmin, Wadebridge and St Austell.
The store has since been said to have been severely damaged, with around 30 per cent of stock destroyed.
Specialist engines from Launceston and St Austell were also called in, as well as water carriers from Liskeard and Wadebridge and a hydraulic platform from Devon and Somerset Fire and Rescue Service.
By 2am the building, measuring 70 metres by 30 metres, was heavily smoke-logged and firefighters, wearing breathing apparatus gained entry.
Smoke was blowing over the A38, causing severe traffic disruption.
Disc-cutters were used on the roller-shutter doors to create additional entry points, allowing firefighters to partly enter the building with a mains water jet.
By 6am crews were using a positive-pressure fan to ventilate the building and monitor internal conditions with the majority of the fire out.