Speaker of the House Nancy Pelosi holds a news conference on the day after violent protesters loyal to US President Donald Trump stormed the US Congress, at the Capitol in Washington, Jan 7, 2021. (J. SCOTT APPLEWHITE / AP)

WASHINGTON - US House Speaker Nancy Pelosi on Monday announced plans for establishing an independent "9/11-type commission" to investigate the deadly Jan 6 Capitol riot, two days after former President Donald Trump was acquitted in his second impeachment trial by the evenly split Senate.

Pelosi wrote in a letter to House Democrats that the next step will be to establish an outside, independent 9/11-type Commission to investigate and report on the facts and causes relating to the Jan 6, 2021 domestic terrorist attack upon the United States Capitol Complex ... and relating to the interference with the peaceful transfer of power

"To protect our security, our next step will be to establish an outside, independent 9/11-type Commission to investigate and report on the facts and causes relating to the Jan 6, 2021 domestic terrorist attack upon the United States Capitol Complex ... and relating to the interference with the peaceful transfer of power," Pelosi wrote in a letter to House Democrats.

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"For the past few weeks, General Honore has been assessing our security needs by reviewing what happened on Jan 6 and how we must ensure that it does not happen again," Pelosi wrote, referring to retired Lieutenant General Russel Honore who she tapped to lead a review of Capitol's "security infrastructure" following the riot last month.

"It is clear from his findings and from the impeachment trial that we must get to the truth of how this happened," Pelosi said, adding that the House will also put forth supplemental spending to boost security at the Capitol.

A 9/11-type commission would be established by a statute passed by both chambers of the US Congress and signed into law by the sitting president, said a CNN report, adding that members of the commission would not be elected leaders and would be outside the government.

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The US Senate on Saturday acquitted Trump on the article of impeachment for inciting insurrection leading to the Capitol riot. Five people died in the attack, including a Capitol police officer.