The inauguration of President-elect Joe Biden will take place in a Washington on edge, after the deadly riot at the US Capitol unleashed a wave of fear and unmatched security concerns.
And law enforcement officials are contending not only with the potential for outside threats but also with rising concerns about an insider attack by troops with a duty to protect him.
There have been no specific threats made against Mr Biden.
The nation’s capital is essentially on lockdown.
More than 25,000 troops and police have been called to duty.
Tanks and concrete barriers block the streets.
The National Mall is closed.
Fencing lines the perimeter of the US Capitol complex.
Checkpoints sit at intersections.
The US Secret Service, which is in charge of the event, says it is prepared.
But law enforcement officials have been monitoring members of far-right extremist and militia groups.
They have grown increasingly concerned about the possibility such groups could stream into Washington and spark violent confrontations, a law enforcement official said.
Even in the hours before the event, federal agents were monitoring “concerning online chatter”, which included an array of threats against elected officials and discussions about ways to infiltrate the inauguration, the official said.
And 12 National Guard members were removed from the security operation after vetting by the FBI, including two who had made extremist statements in posts or texts about Wednesday’s event.
Pentagon officials would not give details on the statements.
Two other US officials said all 12 were found to have ties with right-wing militia groups or to have posted extremist views online.
The officials, a senior intelligence official and an Army official briefed on the matter, did not say which fringe groups the Guard members belonged to or what unit they served in.
The officials said they had all been removed because of “security liabilities”.
General Daniel Hokanson, chief of the National Guard Bureau, confirmed that Guard members had been removed and sent home but said only two cases were related to inappropriate comments or texts related to the inauguration.
He said the other 10 cases were for potential issues that may involve previous criminal behaviour or activities but were not directly related to the inaugural event.
Their removal from the massive security presence at the nation’s capital came amid worries from US defence officials about a potential insider attack or other threat from service members following the deadly riot at the US Capitol on January 6 by Trump supporters.
The FBI has been working to vet all 25,000 National Guard in town.
Officials have said the Pentagon has found no intelligence so far that would indicate an insider threat.
But the FBI has also warned law enforcement officials about the possibility that right-wing fringe groups could pose as members of the National Guard, according to two law enforcement officials familiar with the matter.
Over the summer, a man carrying a handgun and an assault rifle was arrested in Los Angeles and charged with impersonating a National Guard member during a protest.
Actual Guardsmen confronted him when they noticed things out of place on his uniform.
