Would it be too extreme to have each package issued with a fireproof tag which was/is reusable after a few shipments. With today's technology add a strip that indicated an extreme temperature had been reached to either show it was the package that caught fire or its proximity to the fire.
Or become more proactive. Use RFID (Radio Frequency ID) tags and a heat sensor. This would involve continual monitoring of all the RFID tags which may not be acceptable with some dangerous goods.