The fire did not set itself.
The original postEdit
Raistlin: We should not go in now, you will find nothing.
Ingos: How do you know this?
Raistlin: This is either an accidental fire, or one done on purpose. If it's accidental, there is nothing of interest. If it was done on purpose, the person who did it destroyed everything he wanted to, or everything he didn't want others to see. Either way, there is nothing. 'Tis not necassary to get in.
BKU: Good point....
Raistlin: It's most likely accidental, there isn't much of a crime rate in Cardia, besides the occasional theif. We shouldn't make such a big deal about it.