No charges over major Adelaide Hills bushfire that destroyed 24 homes

No charges will be laid over the major bushfire in the Adelaide Hills in January which destroyed 24 homes and thousands of hectares of forest and scrub.

Expert fire scene examiners have determined the blaze started within, or immediately adjacent to, an incinerator, but have been unable to pinpoint the exact cause.

"Despite a complex and exhaustive process, the investigators highlighted a number of possible fire causes such as a smouldering fire from the incinerator, spontaneous combustion or a discarded cigarette butt," detective inspector Greg Hutchins said.

Known as the Sampson Flat fire, the blaze was sparked just after midday on January 2.

It threatened several towns in the Adelaide Hills, causing major property and stock losses.

At one stage it had a perimeter of more than 222 kilometres as it burnt through 12,569 hectares over six days.

More than 130 people, mostly firefighters, were injured.

Insp. Hutchins said given the results of the investigation, the fire could not be proven to be a criminal act.

But he said police would reconsider the matter if new information came to light.