U.S. counter-terror officials have grown concerned in recent months about the threat posed by the militant al-Shabaab group and a cell of U.S.-based Somali sympathizers who have traveled to their homeland to "fight alongside Islamic insurgents," the alert reported.
Authorities stressed that the warning was posted as a precaution as part of the massive effort to monitor intelligence traffic and check out all leads in advance of President-elect Barack Obama's inauguration. Officials have warned that the inauguration poses an attractive target for terrorists because of the large crowds descending on the nation's capital and the historic significance of the country swearing in its first black president.
"As always, we remind the public to be both thoughtful and vigilant about their surroundings, and to notify authorities of any suspicious activity," Knocke said.
A senior law enforcement official familiar with the security operations said the Somali alert had been posted to make sure no effort was spared. The official spoke on condition of anonymity because he was not authorized to speak publicly about security matters. The official said authorities have been monitoring suspicious chatter referring to the inauguration in recent days, but as of late Monday night, they felt comfortable with security preparations.
There was an unprecedented amount of security Tuesday, with thousands of law enforcement officers from 58 federal, state and local agencies working together. Sirens keening, squad cars and utility vehicles swept along downtown streets even before dawn, racing to cordoned checkpoints as crowds gathered.
Knocke said officials consistently monitor all threat information, as they always do.
There has been no change in the terrorist threat level, which remains at yellow - or elevated.
Just before 9 a.m. the U.S. Park Police closed the mall between 4th and 14th streets and were directing people to the grounds of the Washington Monument due to the crowd size, Park Police spokesman Robert Lachance said.
In addition, one person was struck by a subway train, prompting Metro officials to close two stations and turn around some trains. Metro has been running at crush capacity since 4 a.m.
D.C. fire and EMS department spokesman Alan Etter said medical personnel were having trouble getting to people quickly around the National Mall because of the throngs of people, but that everyone who has needed help has eventually received treatment.
"Obviously the crush of people downtown is making it very challenging," Etter said. "We're doing the best we can."
Between 4 a.m. until 10 a.m., the fire department responded to more than 60 calls from people falling down or complaining of the being cold, Etter said. About 20 people have been hospitalized.
And just after 10:15 a.m., police stationed near the Agriculture Department began diverting the gridlocked crowds toward the Washington Monument because that section of the mall was inundated with spectators. Frustrated visitors at one point began clambering over concrete barriers, ignoring outmanned police, until a group of military security officials arrived and secured the area.