About $500,000 damage was caused to a hay shed at Laura after a fire possibly started from spontaneous combustion.
The fire was still burning several hours after the alarm was raised about 11am on Thursday at a farm off Stock Route Road on the outskirts of the town.
Smoke from the blaze could be seen from Stone Hut and Wirrabara.
Residents of Laura were being warned that around 11pm on Thursday night, a change in wind direction would occur which would push smoke towards the township.
Country Fire Service crews were at the scene, but were not fighting the fire, instead adopting a policy of containing it and letting it smoulder for the next few days.
The hay shed measured 50 metres by 20 metres and parts of had been reduced to twisted metal.
About 16 fire-fighters, four trucks and a bulk water carrier, as well as private units, went to the blaze.
Incident controller with the CFS Rob Palmer, of the Bundaleer brigade, said the cause was unknown.
“It is bad luck. It is usually caused by spontaneous combustion, but it has to be determined whether this is the case,” he said.
“Weather conditions in the next couple of days may be an issue. It will smoulder for a couple more days.
“There will be crews here tonight and tomorrow monitoring it.”
People with breathing and heart conditions have been urged to close windows and doors and stay indoors.
The Mid North was previously hit by a grassfire at Laura and a housefire at Gladstone.