The accident occurred Tuesday at 7 a.m. as the morning shift was arriving for work inside the permanent ship-lock. Workers were making their way down scaffolding that stands 100 metres (or 40 storeys) high, when the structure collapsed without warning.

The men fell through the air to the bottom of the shaft, while the scaffolding collapsed onto several other workers who were already down there.

Reports said the first injured workers were pulled from the scene within 10 minutes of the accident, while the last person to be rescued was brought out at 12:20 p.m. Four of the injured are said to be in critical condition.

Most of the dead and injured are from Chongqing municipality and Hubei province, where the dam is being built.

The accident was reported by Hubei Daily (Hubei Ribao), Commercial Radio Hong Kong and Sina.com Web site.