Eight people have been confirmed dead in a collapsed subway tunnel in Hangzhou, China's eastern Zhejiang Province, after another body was recovered on Tuesday afternoon, a local official said.

Four sniffer dogs and more than 400 rescuers are still searching for 13 others, whose hope to survive is very slim after being trapped for more than 72 hours, said Cai Qi, mayor of Hangzhou.

Rescuers work at the collapsed road where a subway tunnel was under construction in Hangzhou, capital of east China's Zhejiang Province, Nov. 15, 2008. [Xinhua photo]

A 75-m section of a subway tunnel under construction collapsed Saturday afternoon. Besides those dead or missing, 24 others were injured.

The rescue operation was proceeding very slowly because the mire in the tunnel was "much more deeper and harder" than expected, said Yang Zhongjie, an expert with the rescue team.

"However, we dare not use large excavating machinery, because we are afraid of destroying any bodies," said Yang.

The China Tiesiju Civil Engineering Group Co. Ltd (CTCEG), the subway project contractor, has been working with the social security and civil affairs departments of Hangzhou to discuss compensation with the victims' families, said Zi Baocheng, CTCEG's deputy Party chief.

The victims, mostly farmers from the eastern Anhui Province, apparently received little training before they started to work on the subway project.

Survivor Song Changfa, who suffered a broken leg, said some of his fellow villagers from Anhui had never done construction work before.

"Before they came here (Hangzhou), they were planting wheat in their hometowns," said Song, who said he had done subway construction work in nearby Shanghai.

Song complained that there were fewer supporting rods inside the subway tunnel than at construction sites in Shanghai.

"In Shanghai, there is a supporting pole every few meters. If there were enough poles here in Hangzhou, my colleagues would have a bigger chance to survive," said Song.

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

Fu Meizhen, a local resident, recalled that cracks of 2 to 3 cm wide and a meter long had appeared on the road about a week ago, right where the collapse took place.

Fu's account was confirmed by Ye Zhiguo, a surviving welder.

"The construction company noticed the subsiding and had began to remedy it by paving the roadbed and inserting steel bars. These efforts continued until the collapse," said Ye.