LOUD-HAILERS dangling from government aircraft might be used to warn people of imminent danger in case of a radiation leak from the Daya Bay nuclear power station, it was revealed yesterday. The loud-hailers, trailed underneath helicopters, would be used to broadcast messages advising people to close their windows and avoid drinking water under plans designed to combat a major disaster at the power station. The plans will be rehearsed as part of an emergency response exercise next Thursday and Friday involving 38 government departments. The rehearsal will be monitored by two officials from the International Atomic Energy Agency. The decision-making ability of government officials and the efficiency of its communications network will be carefully monitored. Government Information Services assistant news director, Mr Harold Yau Fook-sang, said that under the plan, radio and television bulletins would be issued immediately to notify the public of any nuclear emergencies in Daya Bay. But people in remote areas where radio or television broadcasts were difficult to receive might be warned by broadcasts from loud-hailers carried by aircraft in the Government Flying Services. It is understood the territory's contingency plan does not require whole-scale evacuation of residents. Key points of the plan require that all water sources and fresh produce from the mainland be checked for acceptable radiation levels. The border wouldbe closed as a last resort. The drastic measures would be required in case of a major disaster which would see radioactive gas clouds drifting towards Hongkong. However, Royal Observatory officials have maintained normal wind directions would take such clouds away from the territory. International Atomic Energy Agency guidelines say that a 10-kilometre radius around Daya Bay, 50 kilometres northeast of Hongkong, would be in immediate danger. Such broadcasts would only come after the Government confirmed the information from the Daya Bay nuclear power station operators, Mr Yau said. The first to be notified of any disaster would be the Secretary for Security, who would then dispatch the information to Government Information Services, Mr Yau said. However, officials must confirm the situation before the news could be released. ''It is important for the public to know quickly the accurate information. It is the panic factor that we want to avoid and then there is the safety factor. If it is a minor thing, we don't want to upset the public,'' Mr Yau said. He estimated that officials may take up to several hours before confirming the data, but it would only take a minute to release the information to all news organisations in the territory. Once confirmation is received, the Security Branch is then responsible for implementing the Government's contingency plan. The worst-case scenario envisioned under the plan is the evacuation of a handful of residents from Ping Chau which is approximately10 kilometres from Daya Bay.