Bussman NON-35 fuse fire?

[gashmore]

Tenant reported that his fuse box caught fire. I found this stove circuit pullout. This unit was built in the 60s wired in aluminum but I found no corrosion and no indication of foil or other foreign material in the box.. The fuses are Bussman NON-35 Amp. Probably the original fuse from the 50s. I installed a new breaker box.
Never seen or heard of this. Any suggestion what happened?

 

[Lucien Nunes]

Most likely cause is that high resistance had developed at one of the fuse end caps, which began to arc and burn material away until enough heat was being generated to scorch the phenolic moulding. There is a notch in the end cap that suggests it was the fuse element arcing to the end cap, although I suspect the initiating failure was more likely to be high resistance to the pull-out contact.