TWO men are feared dead after they were buried under tonnes of steel reinforcement in a Western caisson yesterday. The pair were 18 metres below ground on the site of a new flyover linking Smithfield and Pokfulam roads when the accident occurred. One worker was identified as Lee Cheung-kwan, 36. The other is believed to be a 24-year-old Vietnamese. Colleagues heard a loud bang at about 3.45 pm as dozens of 12-metre steel rods that were surrounding the chamber broke free and toppled inside. The steel is thought to have hit the men and hurled them 20 metres to the bottom of the caisson, where five metres of concrete had just been laid. Early today, rescue workers had managed to get within four metres of the concrete, but there was no sign of the men. Officials said it would take another 10 hours to clear the steel debris. Assistant fire services commander Leung Kam-tak said the operation had been very difficult. 'Only two firemen can be lowered in at a time,' he said. Firemen trying to cut a way through the tangled mess of steel, were also hampered by fears of setting fire to inflammable material inside the caisson. At one point, construction workers used to handling the 3.8-centimetre rods were sent down to speed up the effort. The caisson is part of the flyover foundation. Construction of the 800-metre flyover started in February and is expected to be completed by June 30, 1997.