The baseline level went from A to B, although most military installations -- including the Pentagon -- were already at a slightly higher level of protection than level A. There are four levels, A through D.
Army Col. Steve Warren says the increase was not triggered by a specific event. He says it was due to a generally heightened threat environment, which would include the recent terror threat and attempted attack surrounding a provocative cartoon contest in Texas.
The alert level was approved by Adm. Bill Gortney, head of U.S. Northern Command.
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