They were due to failure to comply with classification rules, something which as often as not was deliberate in order to save considerable expenditure on tests or additional costs relating to conditions of carriage, or because some shipping companies did not accept goods classified in the most dangerous divisions.
Ils étaient dus au non-respect des règles de classification, le plus souvent délibérément pour économiser les frais importants liés aux épreuves ou les surcoûts liés aux conditions de transport, ou parce que certaines compagnies maritimes n'acceptaient pas les marchandises classées dans les divisions les plus dangereuses.