How do firemen know the cause of a fire after everything has burnt down?

Question

Often times you hear about the cause of a fire being a cigarette for example. However, isn’t the cigarette already long gone after the house/forrest/etc. has burnt down? How is it still possible find out what started the fire?

In: 567

Answer 1

I have no idea but I feel like they just walk around until they see a melted electrical wire and then say, ‘AHA! Electrical fault’.