Halifax Explosion. At 8:45 AM, 6 Dec 1917, at the height of WW 1, the Belgian Relief vessel Imo, through human error and negligence, collided with the French munitions carrier Mont Blanc in the narrowest part of Halifax harbour. Sparks generated by the collision ignited benzol stored on Mont Blancs deck; the burning liquid then seeped into the holds,where it lit 2766tns of picric acid, TNT and guncotton. At 9:06 the munitions ship blew a mile high in the worlds greatest man-made explosion before Hiroshima. Over 2.5 kms of Halifaxs industrial Northend was totally levelled.