Story highlights Total security costs could top $100 million

About 28,000 personnel from dozens of agencies and departments on duty

(CNN) The full force of the US domestic security apparatus will be deployed to stand guard as President-elect Donald Trump takes the oath of office Friday, with an estimated 900,000 people expected to gather in Washington for the inauguration and related activities.

More than 100 square blocks -- about 2.7 square miles -- will be closed to automobile traffic as federal, state and local authorities create a protective bubble around the swearing-in ceremony, presidential festivities and opposition protests. The final tab is expected to surpass $100 million.

Homeland Security Secretary Jeh Johnson said last week at a briefing from a suburban command and control center that an estimated 28,000 in personnel from the US Secret Service, Transportation Security Administration, FBI, US Park Police, US Capitol Police, Coast Guard and local police from Washington and around the nation would be fanned out across the city to provide multiple layers -- and dimensions -- of security.

Lone wolf threat is DHS focus as 99 groups plan pro- and anti-Trump rallies

Despite the absence of a "specific, credible threat," Johnson told reporters the primary focus would be on "individual acts of violent extremism and those who self-radicalize," as have been seen in recent attacks in France and Germany. Dump trucks and buses will be placed in strategic locations to block off large gatherings of pedestrians.

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