BEIJING, March 29 (Reuters) - A Beijing subway tunnel being built for the 2008 Olympics has collapsed, burying six workers who are feared dead, the latest in a series of cave-ins and floods to hit the line.

The accident happened on Wednesday at a tunnel designed for a station exit, leaving a huge hole in the pavement above.

"There is both concrete and earth above the workers so the chances of survival are almost zero," the Beijing News quoted a construction worker as saying.

A contractor had tried to conceal the collapse from authorities by sealing off the site and confiscating the workers' cell phones, it said, citing rescuers.

The 25-km (15-mile) line has reported several floods and cave-ins in the past. Two people were killed in a collapse in June.

In January last year, a section of highway running past Beijing's central business district caved in, rupturing a sewage pipe and flooding a subway construction site.

Beijing is spending $40 billion to prepare for the Olympics, much of it on big ticket transport items for the traffic-snarled city. It plans to add 84 km of new subway lines by August next year.

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