Hong Kong is well served by its two power companies and a massive US-style blackout could not happen, according to the government and the two power giants - Hongkong Electric and China Light and Power. They said the electricity supply had proved 99.99 per cent reliable in recent years. Both power companies had sophisticated systems in place to minimise risk of major supply interruption and to deal with any emergency. A spokesman for the Economic Development and Labour Bureau said the power supplies of the two power companies were regularly monitored by the Electrical and Mechanical Service Department for compliance with the best operational requirements and engineering practice. 'The standard of reliability of electricity supply in Hong Kong achieved by the two power companies is recorded as one of the highest in the world,' he said. Many key services such as health care, banking and public transport, including the airport, had back-up systems.