Imran Ladia, 41, and Sandrianto Julkifli, 22 died on the spot while Risali Lapariama, 25, was believed to have died a few hours later following the 8am incident at the Sepanggar Bay jetty on Monday.
The other victims, La Hebo La Dia and La Suba Bin Ahmad, both 25, as well as La Ellie Bin Lamoane, 30 are receiving treatment at the hospital after they fainted following the incident.
All worked for QL Deep Sea Fishing.
City police chief Asst Comm M.Chandra said prior to the incident, a worker had gone to the jetty to handle some matters when he saw five men lying unconscious at a fish storage deck on the ship.
"The workers on the boat had just returned from their week-long fishing at sea just after midnight on Monday and were planning to get all their catch out," ACP Chandra said.
Upon opening the storage, the first man fainted and his friends went over to help but they too fell unconscious, he said.
"One of them, La Hebo managed to get out alive to call for help," he added.
State Fire and Rescue Department director Nordin Pauzi said investigations showed that the victims had inhaled a large amount of hydrogen Sulfide, a colourless, poisonous, corrosive and explosive gas that reeks of rotten eggs.
He said the gas emitted was a chemical reaction from the fish that were kept without proper ventilation for too long.
“Our team cleared all the drums of rotten fish to ensure no dangerous gas lingers,” he added.
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