Chief Executive Donald Tsang Yam-kuen has the power to activate the highest level of emergency response, including the evacuation of a large number of Hong Kong residents at risk overseas as a result of natural disaster or social unrest. The chief executive's powers are outlined in the Government Emergency Response Operations plan, issued last last year. Mr Tsang would assume command of responses to an overseas incident if it were declared a 'Tier Three', incident. According to the plan for Emergency Response Operations Outside the Hong Kong SAR, the chief executive, or in his place, the chief secretary or secretary for security, would personally activate the highest-level response. But overall responsibility for the handling of an external emergency affecting Hong Kong lies with the chief executive. The plan was set up to help Hong Kong travellers on package tours or self-arranged trips at risk in major external emergencies such as a tsunami, terrorist bombings, aircraft hijacking or civil unrest overseas. The plan came about after the 2004 tsunami killed hundreds of thousands of people in Southeast and South Asia, and security chief Ambrose Lee Siu-kwong told the Legislative Council in 2006 that the government was planning measures to assist travellers in package tours or self-arranged trips in emergency situations. An incident involving low risk to Hong Kong residents overseas would be designated by the Assistance to Hong Kong Residents unit of the Immigration Department a 'Tier One' incident. Where the significance to or impact on residents was considered medium, the department would recommend that the Security Bureau treat it as a 'Tier Two' incident. The chief executive and the chief secretary would be kept notified by the bureau, which would monitor the situation. The Information Services Department would play a similar role. If any situation threatening Hong Kong residents worsened or represented high or extreme risk, the bureau's emergency support unit - headed by a deputy permanent secretary - would recommend that the security chief treat it as a 'Tier Three' incident. Then the chief executive or, under his authorisation, the chief secretary or security chief, could activate a 'Tier Three' response. In the event, the chief secretary would head an emergency monitoring and support centre to co-ordinate different departments and non-governmentals organisations,such as airlines. Dedicated hotlines to help the public would be set up in addition to the Immigration Department's hotline 1868.