Janet and Dick Parker's 1940s Art Deco building on the town's main street was well ablaze when emergency services arrived about 5.15am.
The couple, who have lived in Ranfurly for almost 25 years, owned and operated two businesses within the building, lived in an apartment upstairs, and leased a section of the property to another business owner.
Fire safety investigator Michael Cahill, of Invercargill, conducted the initial fire cause and origin investigation of the building.
Mr Cahill said he determined the fire began in an area of the smoko room inside Mr and Mrs Parker's Ranfurly Auto workshop.
The cause of the fire was still not known, but it was not being treated as suspicious.
Investigations would continue, and Mr Cahill hoped to talk to insurance assessors once they had examined the property.
"I still have to sit down and have another good look at the photographs taken and go over all the information again . . .
"I'll hopefully talk to the insurance assessors to see if they found anything different, and we'll go from there," he said.
No-one was injured in the fire, which was believed to be the largest structural fire in Ranfurly for at least 30 years.
About 25 firefighters from Ranfurly, Naseby, and Omakau battled the blaze.
Mr and Mrs Parker's Ranfurly Bike Hire business was also burnt, but a computer and files were salvaged and the couple planned to continue operating the company from an alternative site.
Waipiata resident Debbie Heron ran her Salad Bowl business from the Parkers' building, and the business was destroyed.
An adjoining cafe suffered smoke and water damage.
Members of the wider Maniototo community were quick to rally around those affected, offering household items, food, accommodation, and other forms of assistance.
