BEIJING - THE final death toll from the collapse of a subway tunnel that was under construction in eastern China has reached 21, with all hope gone of rescuing 13 missing workers, state media reported.

After more than three days of efforts, searchers were unable to find the 13 missing labourers in the silt-filled tunnel in Hangzhou city, the official Xinhua news agency said late on Tuesday.

It cited rescuers as saying there was 'no chance' of finding them alive.

'If the workers are trapped in the middle of the mire, it may take two or three days for rescuers to reach them. If they are at the bottom, it's hard to say when they can be reached', Xinhua quoted a local official as saying.

Eight people have already been confirmed dead in the accident, which happened on Saturday at a construction site for a subway in Hangzhou.

Altogether 75 metres of a tunnel collapsed, creating a huge crater that also trapped 11 vehicles, including at least one bus.

The victims were mostly rural migrant labourers from the poor eastern province of Anhui who had received little training before they started work on the subway project, according to Xinhua.

One of the survivors also complained that there were fewer supporting rods inside the subway tunnel in Hangzhou than at construction sites in Shanghai, Xinhua said.

China has a dismal work safety record, with thousands of people dying every year in mines, factories and on construction sites. -- AFP