Rescuers have confirmed four people were killed and 17 others missing following Saturday's collapse at a subway construction site in east China's Zhejiang Province.

Search is continuing for the 17 trapped in the provincial capital Hangzhou, said the rescue headquarters chief Wang Guangrong.

Rescuers had updated the number of the missing workers from the previous 18 to 17 after they recovered another body at about 10 pm yesterday, which brought the death toll from three to four.

The accident happened at 3:20 pm on Saturday when a 75-meter-long section of the subway tunnel under construction collapsed at the Fengqing Avenue in Xiaoshan District, trapping at least 50 workers and creating a huge crater where 11 vehicles were trapped.

Most of the trapped workers were taken out safely and 26 injured workers were hospitalized. Nine of the injured had been discharged from hospital and the other 15 are still receiving treatment.

More than 1,000 policemen and fire fighters participated in the rescue work. They are pumping water from the tunnel as water from a nearby river flowed into the tunnel soon after the cave-in.

"There is a slim chance for the trapped workers to survive because of heavy flooding in the crater," said Wang, adding that the water level once reached six meters at its highest.

The construction undertaker, China Railway Construction Group Co., Ltd., has halted all the subway construction works in the city for safety checks, said the group's vice president Bai Zhongren.

The provincial work safety bureau and construction bureau have set up an investigation group to find out cause of the accident.

And a panel, composed of experts from Beijing Jiaotong University, Beijing Urban Engineering Design and Research Institute Co., Ltd. and Zhejiang University, is working on the rescue operation scheme.

Under the expert panel's advise, authorities have evacuated three households living near the cave-in site. Their houses will be dismantled to make way for the mechanical operation in rescue and repair work, Bai said.

The families of the dead and the trapped workers are heading to the rescue site.