House Speaker Nancy Pelosi says that Congress will establish an independent commission to investigate the causes of the Jan. 6 storming of the U.S. Capitol by right-wing extremists and other supporters of then-President Trump.

The riot aimed to disrupt congressional certification of President Biden’s Electoral College victory over Trump.

"To protect our security, our security, our security, our next step will be to establish an outside, independent 9/11-type Commission," Pelosi announced on Monday.

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The Speaker, in a letter to House Democratic colleagues, emphasized that the step was needed in order to "get to the truth of how this happened."

Five people, including a Capitol police officer, died as a result of the attack on the building.

WASHINGTON DC, DISTRICT OF COLUMBIA, UNITED STATES - 2021/01/06: Pro-Trump protesters and police clash on top of the Capitol building. Rioters broke windows and breached the Capitol building in an attempt to overthrow the results of the 2020 election. Police used batons and tear gas grenades to eventually disperse the crowd. Rioters used metal bars and tear gas as well against the police. (Photo by Lev Radin/Pacific Press/LightRocket via Getty Images)

The commission will "investigate and report on the facts and causes relating to the January 6, 2021 domestic terrorist attack upon the United States Capitol Complex… and relating to the interference with the peaceful transfer of power, including facts and causes relating to the preparedness and response of the United States Capitol Police and other Federal, State, and local law enforcement in the National Capitol Region," Pelosi wrote.

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"We must put forth a supplemental appropriation to provide for the safety of Members and the security of the Capitol," Pelosi stressed, pointing to security review of the Capitol insurrection compiled by retired Army Lt. Gen. Russel Honore.

"It is clear from his findings and from the impeachment trial that we must get to the truth of how this happened," Pelosi added.

There have been bipartisan calls for a commission on the causes of the Capitol insurrection, similar to the one Congress established following the Sept. 11, 2001 terrorist attacks.

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Trump was acquitted Saturday of one count of inciting the attack on the Capitol. The former president was impeached by the House on Jan. 13, with 10 Republicans joining all 222 Democrats in the chamber in voting to impeach, and 197 Republicans opposing impeachment.

On Saturday, seven GOP senators joined all 50 Democrats in the Senate in voting to convict Trump. The tally was 10 votes shy of the 67 needed to convict Trump.

Fox News Kelly Phares contributed to this report