House Speaker Nancy Pelosi said on Monday that the US Congress will establish an outside, independent commission to review the “facts and causes” related to the deadly 6 January insurrection at the US Capitol by supporters of Donald Trump in the waning days of his presidency.

Pelosi said in a letter to members of Congress that the commission would be modeled on a similar one convened after the 11 September 2001, terrorist attack on Washington and New York.

Democratic and Republican lawmakers had issued calls for a bipartisan 9/11-style commission to investigate why government officials and law enforcement failed to stop the attack on the Capitol in January, while both chambers of Congress were engaged in the process of certifying Joe Biden’s election victory.

The calls followed Trump’s acquittal in his second impeachment trial, in which he was accused of inciting the insurrection after months of stoking his supporters with exhortations to try to overturn the election result and an inflammatory rally on the day itself, outside the White House, when he urged angry supporters to march on the Capitol.

Pelosi said on Monday that the panel will also look at the “facts and causes” behind the catastrophe, in which five people died on 6 January, including a police officer, many were injured, and two police officers died by suicide in the days that followed.

There were renewed calls from both parties on Sunday for such a commission.

“We need a 9/11 commission to find out what happened and make sure it never happens again, and I want to make sure that the Capitol footprint can be better defended next time,” said Lindsey Graham, a Republican senator of South Carolina and close Trump ally who voted to acquit the former president on Saturday. “His behavior after the election was over the top,” Graham said of the former president on Fox News Sunday.

Democrat Chris Coons of Delaware agreed. Speaking on ABC’s This Week, he said that a bipartisan commission would “make sure we secure the Capitol going forward and that we lay bare the record of just how responsible and how abjectly violating of his constitutional oath Trump really was”.

Pelosi’s statement on Monday referred to a review that has been underway, led by retired US army general Russel Honoré.

Pelosi said: “For the past few weeks, General Honoré has been assessing our security needs by reviewing what happened on January 6 and how we must ensure that it does not happen again … It is clear from his findings and from the impeachment trial that we must get to the truth of how this happened.”

She continued: “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 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.”