Houses keep catching fire, why?

I'm very unsure why... but my houses on my island keep catching fire.
I've got the fire department all over so the fire never spreads beyond 3 houses if I'm unlucky, but I just don't get why they keep popping up in the first place.
Is it because of the density maybe? I can't find anything on the internet about this (I probably didn't search properly though somehow).
Sorry for the low image quality, Anno 1602 doesn't take kind to Alt + Tab and taking a screenshot otherwise was impossible.
Best Answer
There is always a chance that houses will catch on fire. However chance increases when there is stagnation in development.
If you reach Merchants/Aristocrats fires will become very rare.
Good strategy would be not to spam a lot of wooden houses and refuse them to use tools for upgrade, but rather buy tools from merchants and give people hope to become higher class.
Less houses - less chance of fire. Better developed houses - less chance of fire.
And also don't fight aborigines, or else they will curse you and fires/volcanoes/diseases/droughts will happen more often.
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What is the most common reason for house fires?
Cooking. The number one cause of house fires is unattended cooking. Make sure that you stay in the room while you are cooking with a heat source.What are the 3 main causes of fire?
For a fire to start it needs a source of ignition, a source of fuel and a source of oxygen. For example, if a smoker falls asleep with a cigarette still lit, and sets fire to the sofa, the cigarette is the source of ignition, the material on the sofa is the source of fuel and the air is the source of oxygen.Woman's Own Surveillance Camera Catches Her Setting Neighbor's Home on Fire: Officials
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Answer 2
First off all you can just press print abf and paste it into paint later.
As far as i know houses have a random chance to ignite simulating a cooking fire that spreads or somthing like that.
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