There are three main categories of how wildfires start, namely Natural, Accidental, and Intentional.
a) Natural fires include lighting strikes, rock falls, and self combustion. There are parts of the country that are prone to lightning fires, while other areas have rocks that are able to make sparks when struck against each. Self combustion veldfires, those which start due to a build up of heat within the fuel load (such as compost heaps, straw bales, etc.) are rare in South Africa.
b) Accidental fires can be caused by faulty electric power lines, electric fences, broken glass, unattended or unsupervised cooking / heating fires, faulty equipment that shoots out sparks, old steam trains spewing out embers, discarded burning cigarette butts, bullets hitting rocks, fireworks, blasting, flares, prescribed burning, and children playing with fire.
c) Intentional fires may be started to commit or hide an existing crime, for revenge purposes, or financial gain (insurance, service provider, overtime, etc). There is also a mental illness aspect where some people cannot help but to start fires to get a thrill from seeing flames. There are also others who set, report, and then assist in fighting the fire in the hope that they will receive recognition as a hero.
See – The Criminal Element in INTRODUCTION TO WILDFIRE INVESTIGATIONS