A WORKER was injured when a World War II bomb exploded as it was found by a dredger off Tsing Yi island yesterday morning. Police bomb disposal officer Mr Dominic Brittain said the engine room and the dredging head of the 106-metre Ham 308 were extensively damaged in the blast. Mr Jose Pelayo, 42, sustained head injuries and was taken to Queen Mary Hospital, where he was treated and discharged. Mr Brittain said after inspecting the damage the weapon was probably an aircraft bomb weighing between 114 kilograms and 228 kilograms. ''We believe the bomb was dropped by the US or British Air Force during World War II,'' he said. The police commander of marine harbour division, Superintendent Laurence Knox, said the area where the blast occurred was a known spot for unexploded wartime bombs. The incident occurred at about 2.15 am when the 5,613-tonne, Dutch-registered Ham 308 was dredging soil from the seabed. The blast came just a day after a World War II incendiary bomb was set off by a worker digging at a construction site in Yau Ma Tei. About 700 residents in nearby residential blocks were evacuated after the phosphorous in the device came into contact with air, sending up plumes of billowing smoke.