The US Capitol is in lockdown after protesters breached barricades amid violent clashes between President Donald Trump's supporters and Washington DC police.
Both chambers of Congress abruptly recessed as they were debating the Electoral College vote that gave Joe Biden the presidency.
There was confusion in the House chamber as the Capitol doors were locked and debate was suspended.
A representative from the Capitol police spoke from a lectern on the dais and told politicians to remain calm, and that more information would be available soon.
An announcement was played inside the Capitol as lawmakers were meeting and expected to vote to affirm Joe Biden's victory.
Due to an "external security threat," no one could enter or exit the Capitol complex, the recording said.
The skirmishes occurred outside in the very spot where president-elect Biden will be inaugurated in just two weeks.
Protesters tore down metal barricades at the bottom of the Capitol's steps and were met by officers in riot gear.
Some tried to push past the officers who held shields and officers could be seen firing pepper spray into the crowd to keep them back. Some in the crowd were shouting "traitors" as officers tried to keep them back.
A suspicious package was also reported in the area, Capitol Police said.
The skirmishes came just shortly after President Trump addressed thousands of his supporters, riling up the crowd with his baseless claims of election fraud at a rally near the White House on Wednesday ahead of Congress' vote.
"We will not let them silence your voices," Mr Trump told the protesters, who had lined up before sunrise to get a prime position to hear the president.
Please support our Capitol Police and Law Enforcement. They are truly on the side of our Country. Stay peaceful!
— Donald J. Trump (@realDonaldTrump) January 6, 2021
Members of Congress inside the House chamber were told by police to put on gas masks after tear gas was dispersed in the Capitol Rotunda amid the skirmishes.
Law enforcement instructed politicians to retrieve masks from under their seats amid the clashes.
After seemingly egging on the protests, President Trump tweeted to his supporters to "stay peaceful" as they violently clash with law enforcement and breached the Capitol building.
The Department of Homeland Security is sending additional federal agents to the US Capitol to help quell the violence.
A spokesperson told the Associated Press that officers from the Federal Protective Service and US Secret Service agents are being sent to the scene.
He said they were requested to assist by US Capitol Police.