Safety measures were ignored when four dock workers entered a tank filled with poisonous gas and two were killed, a Labour Department official said yesterday. A preliminary investigation into Thursday's accident revealed that procedures appeared to have been breached. The four workers went inside an enclosed and poorly ventilated buoyancy tank filled with poisonous gas, without proper supervision or equipment. Work at the dock where the accident happened has been suspended pending outcome of the investigation led by the Marine Department. Wong Fat-kee, the Labour Department's superintendent of factory inspectors, said the company, Universal Dockyard Ltd, could be held responsible if it was proven safety rules were violated. 'Had regulations been properly enforced, would the accident have occurred?' he asked. The tank is one of four mounted on a floating dock in a Yau Tong shipyard, which has been used for boat repairs and building underwater walls. Regulations require the presence of a safety officer to test the air contents of an enclosed space such as the tank where the accident occurred. If the air is found to contain poisonous gases, or insufficient oxygen, the supervisor is required to suspend work and improve air quality. Otherwise he must instruct workers to wear breathing apparatus. Mr Wong said none of the procedures seemed to have been followed. He added that there might not have been any safety officer on hand. Universal Dockyard agreed to release $100,000 to the families of the dead workers and to arrange to bring their mainland wives to Hong Kong to claim the bodies. The company met the Labour Department and the Christian Industrial Committee yesterday. Tsoi Lai-ling, of the Christian Industrial Committee, said mainland workers had the same rights as local ones, and the Government and their employers must not be allowed to neglect them. A inter-departmental summit will be held on Tuesday to discuss industrial safety. The United Christian Hospital, where the two injured workers were treated, said the victims suffered from inhaling poison. A 21-year-old worker was in stable condition last night after suffering chemical burns in an accident at a dying plant in Castle Peak Road.