The week before Joe Biden’s inauguration, downtown Washington looks like a city preparing for war. A huge swath of the city core is blocked off, patrolled by uniformed National Guard forces as part of a buildup not seen since the Civil War. And the U.S. capital is getting even more fortified as federal, state and local officials brace for a worst-case scenario of violence tied to the Jan. 20 inauguration. More than 25,000 law enforcement, military and intelligence personnel have been activated to provide security in Washington leading up to President-elect Biden’s swearing-in, a ceremony that will have far less pomp than in the past because of the Covid-19 pandemic and last week’s deadly riots at the Capitol. Behind the scenes, federal agents, prosecutors and analysts are racing to track and disrupt active plots in what some say is the greatest security challenge since the days after the Sept. 11, 2001 terrorist attacks, according to current and former U.S. officials. “We’re concerned about the potential for violence at multiple protests and rallies planned here in D.C. and at state capitol buildings around the country in the days to come,” FBI Director Christoper Wray said in a security briefing on Thursday. “It could bring armed individuals within close proximity to government buildings and officials.” A bulletin by the FBI and other agencies this week warned that extremists targeting the inauguration may exploit the aftermath of the Jan. 6 Capitol breach by conducting attacks to destabilize and force a larger conflict in the U.S., according to a person familiar with it. The bulletin also warned that the siege of the Capitol will be a “significant driver of violence” in the future, the person said. More than 100 people involved in the riots -- which led to at least five deaths -- have been charged with crimes so far, with more expected. Efforts to uncover active plots include searching social media, monitoring online chat sites, arresting individuals identified in the Capitol riots and interviewing suspects and witnesses, two U.S. officials said. The Justice Department also has started making preemptive arrests: An Illinois man was arrested on Jan. 12 for threatening to kill Democrats during the inauguration. Capitol Police have warned that anyone trying to “unlawfully gain access” to the Capitol Complex will be subject to “an appropriate use of force and arrest.” A presidential inauguration is always a highest-tier security affair, but agencies amplified and accelerated their operations following the Capitol siege, which was led by Trump supporters trying to disrupt the certification of Biden’s Electoral College victory by Congress. The Secret Service is in charge of inauguration security and has activated a command center -- officially known as the Multi-Agency Coordinating Center -- to bring together federal, state and local agencies. More than 20 public safety agencies are involved in the security planning, including law enforcement, fire and rescue and emergency medical services, according to the Secret Service. The FBI has command centers at its headquarters and its Washington Field Office and is leading the Joint Terrorism Task Force to share intelligence and threat information between agencies, including with the Capitol Police, Park Police and the Metropolitan Police Department. Along with the physical fortification of the Capitol, the D.C. government has closed a large section of the city to traffic, shut down subway stations and detoured public buses. The National Mall, the traditional gathering point for crowds on inauguration day, may also be closed under a plan being considered by the National Park Service. Outside Washington, the FBI established command posts in all of its field offices across the country and has encouraged state and local officials to share any intelligence they pick up about threats. The FBI and Justice Department have stood up a strike force to pursue charges of sedition against anyone who carries out attacks. Subscribe to our YouTube channel: https://bit.ly/2TwO8Gm Bloomberg Quicktake brings you live global news and original shows spanning business, technology, politics and culture. Make sense of the stories changing your business and your world. To watch complete coverage on Bloomberg Quicktake 24/7, visit http://www.bloomberg.com/qt/live, or watch on Apple TV, Roku, Samsung Smart TV, Fire TV and Android TV on the Bloomberg app. Have a story to tell? Fill out this survey for a chance to have it featured on Bloomberg Quicktake: https://cor.us/surveys/27AF30 Connect with us on… YouTube: https://www.youtube.com/user/Bloomberg Breaking News on YouTube: https://www.youtube.com/c/BloombergQuickTakeNews Twitter: https://twitter.com/quicktake Facebook: https://www.facebook.com/quicktake Instagram: https://www.instagram.com/quicktake