The Rural Art Deco Gallery was undamaged by the fire but the Catholic Women's League's second-hand clothing business in another wing of the building was badly damaged by water.
The 1940s Art Deco building is owned by the Central Otago District Council but is rented by Rural Art Deco Maniototo. Vice-chairwoman Amie Pont said the fire was horrible and highlighted the importance of the building to the town.
Many people had put a huge amount of work into restoring and maintaining the building and for the fire to possibly have been deliberately lit was ''absolutely disgusting'', she said.
Ranfurly Volunteer Fire Brigade Chief Fire Officer James Hazlett said crews from Ranfurly and Naseby were called to a rubbish fire at 7.20pm in an annex - an ''outback shed'' - joined to the main Charlemont St building.
When the first crew arrived the fire had ''engulfed'' a wall and spread to the ceiling of the shed. There were concerns northwesterly winds would fan the fire to the main building. Two ground floor rooms were damaged by water and three upstairs by smoke.
Eighteen firefighters were on site for about two hours, Mr Hazlett said.
The fire was being treated as suspicious and a fire investigator would be on site today.
He wanted to talk to a cyclist on the Otago Central Rail Trail who discovered the fire.
''We've been told he tried to put the fire out and then went to a hotel and raised the alarm. We are trying to track him down to say thanks,'' Mr Hazlett said.
