Zhang Di was pleading desperately with firemen yesterday to save his older brother. "He's only 23 years old and his son is only four months," he cried.

Zhang Peipei is among the 17 people still missing after an under-construction subway tunnel collapsed in Hangzhou on Saturday afternoon.

Zhang Di, too, was working at the site, but fortunately he had been sent on errand when the accident took place.

Four workers have been confirmed dead in the accident that took place in Xiaoshan, a Hangzhou suburb.

State leaders, including Premier Wen Jiabao and Vice-Premier Li Keqiang, have ordered that no efforts should be spared to look for the workers still missing.

"We should rescue the wounded and do everything for the safety of the injured and the missing at all costs," said a directive from the State leaders, according to Zhejiang Television.

"Causes of the accident should be investigated thoroughly and the findings made clear as soon as possible," the directive said.

The workers who survived the incident are still in a state of shock. Fang Fuze, 41, burst into tears when reporters approached to interview him.

"We tried to use the crane to pull our colleagues out… But there were so many of them inside (the crater) and some could not grip the crane and fell into the crater again.

"We could hear them calling for help from the bottom of the crater but we could do nothing to help them," he said.

Local authorities have arranged for accommodation for the relatives and friends of the dead and missing who have gathered at the accident site. Compensation packages for death and injuries will be announced soon, officials said.

About 2,000 rescuers are searching around the clock for the missing people. But the most optimistic estimate says it could take up to three days to complete a thorough search because the collapsed stretch of the road has taken with it machines, vehicles and building materials, said Chen Yunmin, head of the architecture department of Zhejiang University.

The professor, also a member of the accident emergency rescue team, said workers were working to move the collapsed steel columns because only after they do so would a rescue team be able to dig underground.

"According to the current progress it would take at least another three days, therefore the chances of the missing people still being alive is very slim," Chen said.

The subsidence has caused cracks in some nearby buildings, creating fear among people living or working in them, Zhejiang TV said.

Four houses have to be pulled down soon and the residents moved elsewhere.

The nearby Xiangchao primary school, too, has been damaged. Students were told to take a day off on Monday, according to a school official, Cai Renlin. All the 35 subway construction sites in Hangzhou stopped work yesterday to enable experts to conduct underground safety checks to rule out any potential risks.

Questions:

1. How many people died and how many are still missing?

2. According to worker Fang Fuze, why did they have trouble trying to rescue their colleagues?

3. What does Chen Yunmin, a member of the accident rescue team say must be done before rescue crews can go underground?

Answers:

1. Four dead, 17 missing.

2. Because there were so many of them, they could not hold onto the crane and fell back into the crater.

3. Steel columns need to be removed first, which could take three more days.