Investigators are examining how toxic gas accumulated in a ballast tank of a ship that held a gas-free certificate, after 10 workers died at Ferdous Steel Ship Recycling Industries in Bhatiari, Sitakunda, on August 14. The gas spread when flame cutting began in ballast tank No. 3, following the completion of cutting work on tank No. 4 and much of the vessel over about 10 months.

Government investigation committees have collected samples of liquid, air and chemical materials from the affected tank and sent them to laboratories in Dhaka. Officials involved in the inquiry said the gas source cannot be confirmed before laboratory reports arrive. Investigators are considering whether gases such as hydrogen sulfide formed through decomposition of trapped water, or whether heat from cutting caused another chemical reaction.

The vessel had obtained a gas-free certificate from its original owners when it was purchased from Dubai, and approvals were obtained from relevant departments after arrival in Bangladesh. The inquiry is also reviewing pre-cutting gas tests, ventilation and safety protocols. Former industry representatives called for a scientific determination of the cause and said worker safety cannot be compromised.