Damaged chimneys and homeless people are likely to lead to more abandoned red zone properties going up in flames this winter, firefighters fear.
Fire Service fire risk management officer Mark Thomas said homeless people would soon be moving into abandoned homes to keep warm.
If they lit fires where chimneys were damage it could be a recipe for disaster.
"We definitely are very, very concerned. There has been a slow but steady increase of fires in red zone properties. At the moment I would say we are up to about one a week," said Mr Thomas.
"We quite often find evidence in the houses of people living there including bottles, graffiti, bedding and mattresses," he said.