In the name of safety ... mostly if some one is going to use a heat lamb/bulb for warming chickens ...
While it is possible to report that "a heat lamp was the cause of the fire" ... once the coop is just a smoldering pile of ashes ... of course the heat lamp is not still "hanging secured" obviously in the OP's pictures, there would be evidence of the chains ...
What we don't know is where extra chains are not used ... did the fire START because of the clamp??? Or did dust build up on the bulb, ignite ... and fall into the coop litter???
If your gonna use a heat lamp ... for more than a quick cold snap ... like all winter, or even just leaving it our in the coop all the time, but only turning it on occasionally ... make sure you clean the dust off!