Fire ripped through the Lancoona homestead, about 45km north-east of Hillston on the Lachlan River, just before 4am on Wednesday morning, with residents fleeing the house shortly before the blaze took hold.

Forensic police, Essential Energy and RFS investigators are probing the cause of the fire but are not treating it as suspicious.

The damage is estimated to be in excess of $1 million.

Owned by the Helps family for the past three years, the home and accompanying 3150-acre property were previously owned for more than a decade by well-known former Griffith vet David Harding, in partnership with Louise and Neil Flanagan.

"It's just devastating," Mr Harding said.

"It was such a big, beautiful home with such big, thick walls.

"It's hard to imagine it gone."

More than a dozen RFS volunteers from surrounding brigades attended the fire but were unable to save the property.

Police are preparing a brief for the coroner.