Eight people have now been confirmed dead as a result of the Hangzhou subway collapse in China’s eastern Zhejiang Province after another body was recovered on Tuesday afternoon, a local official said. Sniffer dogs and more than 400 rescue workers are still searching for 13 others, whose survival is deemed very slim after being trapped for more than 72 hours, said Cai Qi, mayor of Hangzhou.

A 75-m section of a subway tunnel under construction collapsed at 3.20pm Saturday afternoon (local time), forming a large crater that trapped around 50 workers and 11 vehicles. Some workers were rescued from the crater using a construction crane. However, water from a nearby river then rushed into the tunnel, rising as high as 6m and filling the crater.

Within hours all the vehicles had been removed and 26 casualties rushed to hospital. Since then the rescue operation is said to have been proceeding very slowly due to the highly saturated earth, which is too unstable to support heavy excavation equipment.

Further cracks that have developed in the area over the last 48 hours have lead a school to be evacuated and houses to be torn down for safety. The contractor working on the tunnel, China Railway Construction Group Co, has suspended all subway construction work for the time being.

Zhao Tiechui, deputy head of the state work safety administration, will lead a task force to investigate the cause of the accident. They were told that cracks had started to appear on the road surface and the roadbed had sunk near the construction site more than a month ago.

Local news reports say the victims, mostly farmers from the eastern Anhui Province, received little training before they started work on the subway project.

The 69km long subway project began in March last year and is due to be completed in 2011.