Joe Biden has been safely sworn in as president of the United States two weeks after rioters loyal to former president Donald Trump besieged the Capitol.
Law enforcement officials contended not only with the potential for outside threats but also with rising concerns about an insider attack.
Officials monitored members of far-right extremist and militia groups, increasingly concerned about the risk they could stream into Washington and spark violent confrontations, a law enforcement official said.
There were a few scattered arrests but no major protests or serious disruptions in the city during Mr Biden’s inauguration ceremony.
As Mr Biden put it in his address: “Here we stand just days after a riotous mob thought they could use violence to silence the will of the people, to stop the work of our democracy, to drive us from this sacred ground. It did not happen. It will never happen, not today, not tomorrow, not ever. Not ever.”
After the deadly attack that killed five on January 6, the Secret Service stepped up security for the inauguration early, essentially locking down the nation’s capital.
In the hours before the event, federal agents monitored “concerning online chatter”, which included an array of threats against elected officials and discussions about ways to infiltrate the inauguration, the official said.
In right-wing online chat groups, believers in the QAnon conspiracy theory expressed disappointment that top Democrats were not arrested for sex trafficking and that Mr Trump did not seize a second term.
Twelve National Guard members were removed from the security operation a day earlier 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. The FBI vetted all 25,000 members in an extraordinary security effort in part over the presence of some ex-military in the riot.