An investigation, authorised by the Secretary of State to be carried out by Major Cooper-Key, an explosives inspector, was started soon afterwards and labelled "Accident 379/1916". It revealed that the company was storing twice the amount of picric acid than it was licensed for. This investigation was used during the coroners' inquest into the disaster held in Bradford Town Hall in September of the same year. The issue of the missing Belgians and a sabotage plot was investigated carefully, and the Belgians were all asked to account for their absenteeism on the day. All could give satisfactory explanations for their whereabouts on the day and the jury decided that the disaster was an accident, though they did produce a small note indicating that the company should have been storing their goods properly. The fire was most probably started by the ignition of iron picrate which was on the top of the drums.Picric acid reacts with most metals, but not with tin. The drums were made with iron that was lined with tin. As the drums had no external strops or protective frames (such as wood) the malleable tin was easily worn away exposing the iron underneath which would have reacted with the picric acid to form iron picrate. As iron picrate is sensitive to being struck or hit, this could have been as source of ignition when the drums made contact with the stone setts around the magazines. Another possibility is that the drums caused a spark whilst being rolled across the stone floor.
