A blaze that ripped through two large garages and spread to a bungalow in Derby was accidental, firefighters have said.
Six crews were called to Radford Street, Alvaston, at 18:02 BST on Saturday.
The fire sent a huge plume of smoke into the sky, and people living nearby were urged to keep their windows and doors closed.
The incident was scaled back by 20:45, with two crews and an aerial ladder platform remaining at the scene to "damp down".
Derbyshire Fire and Rescue Service said all occupants of the bungalow were out of the property by the time crews arrived at the scene and no-one was injured.
An investigation on Sunday determined the blaze was "most likely" caused by an unknown fault with electrical equipment in the outdoor garages, the fire service said.