Last Sunday's incident was the first problem of international classification scale to occur at Daya Bay. At least 59 similar incidents had been reported at the plant since last April, well-placed sources told the Sunday Morning Post.

The disclosure of the first classified problem since Daya Bay went on line sparked renewed Hong Kong criticism of China's nuclear power programme and came only days after the announcement of a planned expansion that would site reactors in a ring around the territory.

The mishap also underscored Hong Kong Government efforts to reach an agreement with Chinese officials about expanded information of on-site problems.

The present agreements only bind China to inform Hong Kong about accidents in which there is likely to be an off-site release of radiation that may affect the territory.

''People are very frightened and worried about Daya Bay,'' said Legislative Councillor, the Reverend Fung Chi-wood. ''More plants will add to the worry. Legco should urge China not to build more so close, but I do not know how much they will listen.'' Fears about Chinese secrecy and plant safety are also of international concern. American nuclear energy companies, barred from doing business with China, are closely monitoring the Daya Bay situation.

Officials with the Hong Kong Nuclear Investment Company insist the pump problem has been the only reportable incident at the plant since operation began.

They said most of the other incidents occurred during Daya Bay's testing phase, when equipment was purposefully pushed to the limits to probe the efficiency of safety devices and monitoring systems.

''This is a safe plant,'' said Dr Jacques Pretti, senior nuclear technical adviser with the company.

He said Daya Bay had performed to or above expectations, despite the minor pump problem.

Dr Pretti said automated monitoring equipment immediately detected the pump problem and triggered safety shutdowns.

However, the mishap has renewed calls for a government nuclear watchdog committee to monitor China's growing nuclear power industry. A second reactor is set to come on line at Daya Bay next summer.

Environmental pressure group Friends of the Earth accused Daya Bay officials of secrecy.

''It just goes to show what we suspect about nuclear power, that it's not safe,'' Friends spokeswoman Lisa Hopkinson said.

''If they can't be open and straight about more minor incidents, you wonder whether they will tell us about a real accident.

''We would like to know about all on and off-site accidents. If an accident occurs, what follow-up action is taken? It may be minor but provided operators can respond and deal with it, it provides reassurance. If it occurs with regularity, it is indicative that things are going wrong.'' Although Friends of the Earth believe the chances of a meltdown at Daya Bay are small, the problem lies more in the risks of chronic health problems from radioactivity that may contaminate water and food supplies.

China last week announced plans for several other reactors in Guangdong province, including two just five kilometres from Daya Bay. The mainland intends to build up to six additional reactors at Yangjiang City, about 200 kilometres southwest of Hong Kong.

Chinese officials have talked of a massive investment in nuclear power, with plans to boost nuclear energy production twenty-fold to 20,000 megawatts by the year 2020.