Arizona’s terrorist threat level also elevated to orange Sunday.
"We are going along with the national move to go from yellow to orange," said Jeanine L’Ecuyer, a spokeswoman for Gov. Janet Napolitano.
"We are aware of no specific threat to Arizona."
Homeland Security Secretary Tom Ridge on Sunday raised the national threat level to orange, the second-highest, saying attacks were possible during the holidays and that threat indicators are "perhaps greater now than at any point" since Sept. 11, 2001.
The most visible reaction to the heightened alert is at Phoenix Sky Harbor International Airport.
Deborah Ostreicher, an airport spokeswoman, said she expected the airport to implement stepped-up security directives by this morning.
Security changes could include random vehicle inspections on airport roads and terminals, increased police and security presence, and restrictive barricades to tighten entrances, Ostreicher said.
L’Ecuyer said emergency and security plans are in place for sensitive locations and industries throughout the state.
"The governor has detailed information on critical assets in Arizona," L’Ecuyer said. "The governor feels very comfortable with the level of security at those locations."
Valley fire and police officials said the orange alert mostly means police and fire personnel are on heightened awareness.
Arizona Department of Public Safety officer Steve Volden said DPS commanders will likely implement a threat response plan by this morning.
In the past, that response has been to keep as many officers on duty as possible, limiting vacations and other time off.