Collapse at a construction site left three people dead and one other seriously injured Tuesday in Lanzhou, capital of northwest China's Gansu Province, the local source said.

At around 5:20 PM Tuesday, four migrant workers were dredging an underground sewage conduit in Qilihe district of the city when the 10-meter long tunnel collapsed, trapping all of the four.

Three of them had been suffocated to death when they were scooped out after 40 minutes of digging by rescuers, and the other one survived after receiving treatment in hospital.

(Xinhua News Agency November 16, 2005)