Eight crew and a dockworker had to be decontaminated after being exposed to leaking gas while a cargo of grain was unloaded in Warrenpoint Harbour, Co.Down, a report into the incident has revealed.
The workers were taken to hospital as the fire service cordoned off an area around the quayside when a fumigant retainer began to smoke.
Others, also containing aluminium phosphide, spilled onto the ground as they were being removed from the ship.
The emergency started after the Arklow Meadow docked last December following a 14 day voyage from the Ukraine.
As the grain was unloaded, it became apparent that the fumigant, which had been placed on top of the cargo, was still active, according to a report by the Marine Accident Investigation branch.
The ship's crew was evacuated ashore after retainers which had been collected and placed inside plastic bags, started to smoke.
The eight crew and a stevedore, who had potentially been exposed to the gas, were taken to hospital for observation and decontamination.
A total of 89 fumigant retainers were recovered from the ship and shore area - they were neutralised by immersing them in water - but 21 were unaccounted for.
It took five days for the level of gas in the vessel's cargo holds to reduce to an acceptable level, according to the investigation report.
It also claimed that although Warrenpoint Harbour Authority had reacted quickly, the port had not developed procedures or emergency plans to deal specifically with potential hazards associated with fumigants.
The phosphide had probably remained active due to tight packaging and relatively low humidity in the cargo holds, and although the levels of gas in the atmosphere had been assessed as to have been safe, the fumigant retainers were now removed from the top of the grain cargo before cargo operations started.
The report said: "Onboard procedures for the carriage of fumigated cargoes were scant, and the instructions provided by the fumigator in the Ukraine were not followed."
It added: "A recommendation has been made to the Maritime and Coastguard Agency aimed at improving the guidance available regarding the carriage of fumigated cargoes.
"A recommendation has been made to the British Ports Association and the UK Major Ports Group to help ensure that all UK ports have procedures and emergency plans in place when dealing with fumigated cargoes."