Police and fire service experts are investigating possible links between four recent farm fires in Montgomery, Powys.
Five fire appliances attended the latest blaze, in buildings at Stalloe Farm, Hendomen, which was reported at 1.30am on Tuesday, 11 November.
Just three days earlier about 50 firefighters spent more than 12 hours controlling a major fire at Great Hem Farm, a few miles away at Forden. This blaze badly damaged several buildings, and destroyed a combine harvester and a large quantity of hay and straw.
Barn fires also occurred in September and October at Woodlands Farm, a large dairy unit also near Forden.
There are no reports of injuries to people or livestock at any of the fires.
While the latest blaze is still being investigated, Dyfed Powys Police have appealed to the public and the farming community for information.
Rhian Nowell-Philips, chief policy adviser at the Farmers Union of Wales, said livestock farms with big stores of winter fodder were particularly vulnerable to accidental and deliberately-started fires.
“Our advice is to get guidance from local fire prevention specialists,” Ms Nowell-Phillips said. “When it comes to combatting arson, and we do not yet know if any of these fires fall into that category, it is a question of being very vigilant.
“We also have to be good neighbours and keep our eyes open as we travel rural roads, and be ready to report anything suspicious. The emergency services would far rather deal with an honest mistake than tackle a real fire.