A barn and its contents worth more than $50,000 was razed in Outram at 7.20am yesterday.
Hours later, a $100,000 tractor on a Hindon farm was destroyed in a suspicious blaze that severely damaged the barn the tractor was stored in.
The police believe the fires were linked and lit deliberately.
Police believe the suspects travelled from Outram into George King Memorial Dr where the first fire was lit, before driving to Mount Gowrie Rd and setting the tractor on fire, Senior Sergeant Darryl Lennane, of Mosgiel, said.
"This poses a real risk to all those farms in these secluded rural properties and the actions of this person, or persons, are of great concern to police," he said.
Surveying the wreckage of the hay barn and smouldering remains of his winter feed, farm owner Rob Johnstone said he was disappointed the fire was arson: "It is just needless damage to property."
Mr Johnstone was alerted to the fire at 7.20am by an employee and said the blaze, on a property off George King Memorial Dr, was "a hell of a hot fire".
The barn, along with 1500 hay bales and farm machinery, was destroyed in the blaze.
Neighbours had helped save more hay bales stacked at the side of the barn from being destroyed by the blaze.
Mr Johnstone estimated the damage to be worth more than $50,000, and his insurance company was assessing the property yesterday.
Fire appliances from Outram, Mosgiel and Lookout Point attended the blaze, with a water tanker from the Dunedin City Council used to dampen down some of the still-smouldering winter feed.
With the hay bales being two years old and no power supply connected to the building, Southern Region Fire Safety officer Mike Cahill, of Invercargill, confirmed the fire appeared suspicious.
"It is now a matter for police," Mr Cahill said.
Anyone who had seen suspicious vehicles or people in the Outram or Hindon areas yesterday was urged to contact Mosgiel police on 489-3534.
