United States Department of Homeland Security (DHS)
The DHS in 2002 was founded on the answer of the terrorist attacks of the 9/11/2001 with headquarter in Washington, D.C. Present minister is Janet Napolitano. The DHS works together with 22 existing federal authorities among other with the emergency services authority FEMA (Federal Emergency management agency).
The ministry uses five steps (warning steps) which were already used since the times of the cold war by the US-Military.
See also: http://www.dhs.gov