My friend was passing a neighbour's house when she heard their smoke alarm. They were out (no cars), and she saw b;ack smoke coming out of a bedroom window. She called the fire brigade & the owner. He turned up just after the fire brigade, but they wouldn't let him go in because by that time black smoke was right through the house. So they went in with breathing equipment, and came out a few minutes later with....... a black, very small, chicken in a roasting dish!
Luckily that was it - it had caught fire in the oven & there were no other flames, just lots of smoke. The oven was set at 180 degrees & the owner said it had only been on about half an hour - weird. One of the firemen said that perhaps the thermostat had a fault so the temperature was at full blast. Also, that cheap chicken had a lot of water that mixed with the oil to spit & catch fire. The chicken was completely black & shrunken, but inside wasn't dry.
Anyway, later that day the owner tried the oven & found the thermostat was working fine. He then mentioned that he had taken a frozen chicken from his freezer and had defrosted it inthemicrowave!
So there you go - lots of water, presumably, and another reason not to defrost thick cuts of meat in the microwave. Now I shall also be very wary of leaving the oven on when I go out.
I've made the mistake of microwaving frozen fishcakes in my combination microwave instead of baking them. Result - completely dry, crispy objects (got them out just before they started to burn as well). Very shrunken - rather think that is what happened to OP's friend's neighbour.
Maybe it was heated to a very high temperature inside by the microwave and then by the time it had been in the oven for half an hour the middle of the chicken was so hot it had burnt the rest of it dry and started the fire.
maybe it just touched the element and caught fire? easy enough to do if you're not paying attention when you slide in the shelf? (9t would be JUST liek a man to ruin meat in the micro then jam it onto the top shelf.)