Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Other / Unknown
Deviation / Discrepancy - Procedural Hazardous Material Violation; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
General None Reported / Taken
Human Factors
[Company] Duty Officer informed CA (Captain) and FO (First Officer) (me) via company email that after block-in of a revenue flight from ZZZ-ZZZ1 that ZZZ1 offload crew discovered [Aircraft X] had unmanifested ADG in position 12L. The container at 12L was labeled as IBX (International Box Volume); but actually contained 321 pieces of flammable gas (this info provided via Duty Officer in same company email). It was my understanding based on standardized DG (Dangerous Goods) procedures pre-flight that [Aircraft X] did not have any DG loaded.The cause of Hazmat violation was improper tracking of DG materials. DG unmanifested in non-DG labeled container.I suggest more vigilance and thoroughness when handling; tracking; and loading DG.
First Officer reported undocumented transport of Hazmat cargo due to improper DG tracking.