Rescuers searched Monday for 17 workers missing after a subway tunnel they were building in eastern China caved in, killing at least four people, the state news agency said.

A 250-foot-wide section of road over the construction site collapsed in the eastern city of Hangzhou on Saturday, trapping workers and creating a huge crater into which at least 11 vehicles plunged.

Poor construction quality is a chronic problem in China, and is often blamed on bad planning, shoddy work or theft of materials.

The official Xinhua News Agency said rescuers were pumping out water that had seeped into the tunnel from a nearby river and stood at 10 feet deep.

Four bodies had been recovered as of late Sunday. Those missing were believed to be construction workers, Xinhua said.

"There is a slim chance for the survival of trapped workers because of heavy flooding in the crater," Xinhua quoted Wang Guangrong, spokesman for the rescue team, as saying Sunday.

Xinhua said at least 50 workers were working underground at the time. A total of 26 workers were rescued and sent to a hospital for treatment, it said. Xinhua said four were dead and 17 missing, and did not account for the three additional workers.

Phone calls to the local and provincial work safety bureaus were not answered Sunday.

Wang told Xinhua that rescuers pulled out the vehicles that had plunged into the crater and that all the drivers and passengers were safe. Three houses near the cave-in have been evacuated, Wang said.

The 43-mile subway project, begun in March last year, is being built at a cost of $5.1 billion and is due to be completed in 2011, Xinhua said.

The accident is the latest in China amid a frenzy of subway construction. More than a dozen cities received approval to build new subway systems in recent years, joining those already in use in major cities such as Beijing and Shanghai.