Honolulu firefighters determined today a fire that damaged a new house in Kahala on Thursday was caused by oil-soaked rags that workers had left on the roof.

Honolulu fire Capt. Terry Seelig said the rags were soaked with linseed oil, which heated up in the oxidization process and caused a fire that spread rapidly over the freshly oiled, wood-shingled roof.

The fire burned through a wall and into the living room of the single-story home at 4727 Aukai Ave., causing $200,000 in damage. Firefighters quickly brought the 3:47 p.m. fire under control, but the roof was already significantly damaged.

Seelig suggested those working with drying oils — such as poppy seed oil, tung oil, and walnut oil — lay the oil-soaked rags out flat to dry on a non-flammable surface outside or hanging them on a laundry line, taking care not to bunch them up. Once the rags have dried out, they can be thrown away.