The House Speaker grew emotional as she announced that she has asked retired Lieutenant General Russel Honoré to carry out an “immediate” review security arrangements in the wake of the violence last week.
And Ms Pelosi also warned lawmakers that they could face criminal charges if they were found to have aided the pro-Trump mob.
“If in fact it is found that members of Congress were accomplices to this insurrection, if they aided and abetted the crime, there may have to be actions taken beyond the Congress in terms of prosecution for that,” she said.
Democratic lawmakers are investigating whether members of Congress gave rioters tours of the Capitol in the days before the violence unfolded.
The probe follows speculation that Republican members of Congress and Capitol Police may have played a role organising or enabling a deadly mob in support of Donald Trump’s attempts to overturn the results of the 2020 presidential election he insists was “stolen” from them.
Democratic Congressman Tim Ryan of Ohio, who chairs a Capitol Police oversight committee, has aid that an investigation is looking at more than one lawmaker who gave tours to “handfuls” of people at the Capitol the day before the riot.
“Last week, we suffered a devastating attack on the Capitol that threatened the lives of and traumatised members of Congress, staff and support workers,” said Ms Pelosi.
“To protect our Democracy, we must now subject the security of the US Capitol Complex to rigorous scrutiny.”
Lt Gen Honore Honoré is best known for overseeing humanitarian aid efforts in Louisiana following the devastation of Hurricane Katrina.
Ms Pelosi says he will conduct an immediate review of security, inter-agency interaction and Capitol “command and control.”
“I have asked retired Lieutenant General Russel L Honoré to lead an immediate review of security infrastructure, inter-agency processes and command and control,” Pelosi said Friday morning.
“The general is a respected leader with experience dealing with crisis.”
Federal watchdogs have also launched a review into how the FBI, Pentagon and other law enforcement agencies responded to the attack.
The investigations have been launched by the inspectors general for the departments of Justice, Homeland Security, Interior and Defense, and they will look at how agencies shared intelligence before the riot and how the Pentagon mobilised troops as the mayhem unfolded.
The Capitol Police have said they had prepared for only First Amendment outside the building as lawmakers gathered to certify the election.
The Pentagon has said that the force turned down an offer of help in the days before the riot, despite the violence being publicly coordinated on social media platforms and Mr Trump egging on his supporters.
The probe will also look at what the FBI knew in the run-up to the riot, as an internal bulletin from its field office in Norfolk, Virginia, stated that extremists had threatened to start a “war.”
At least five people, including a US Capitol Police officer and a San Diego woman shot by law enforcement, died in the violence that followed a rally by Donald Trump.
“We’re going to walk down to the Capitol and we’re going to cheer on our brave senators and congressmen and women and we’re probably not going to be cheering so much for some of them,” Mr Trump told them.
“You’ll never take back our country with weakness. You have to show strength, and you have to be strong.”
His supporters then marched to the Capitol before overwhelming police lines and stormed the building to try and prevent lawmakers from ratifying Joe Biden’s election victory.
After a lengthy delay to clear out the rioters the House and Senate returned and certified Mr Biden’s defeat of Mr Trump.
Mr Trump was impeached in the House for “incitement of insurrection” following the mayhem.
The final impeachment vote against Mr Trump was 232 to 197, with 10 Republicans joining all 222 Democrats in supporting the single article of impeachment.
Mr Trump was first impeached in 2019 over his efforts to pressure Ukraine to investigate Mr Biden and his family.