Washington, Feb 16 (IANS): US House Speaker Nancy Pelosi has said the Congress will establish an "outside, independent" commission to investigate the January 6 attack on the US Capitol by the supporters of former US President Donald Trump.

In a letter to lawmakers, she said the commission would be modelled on the inquiry into the September 11, 2001 attacks on New York and the Pentagon, the BBC reported on Monday.

"We must get to the truth of how this happened," she said.

Trump was acquitted by the Senate of inciting the violence. But Democrats and some Republicans have backed an independent probe into the riots, which left five persons dead.

Pelosi said that US Army Lieutenant General Russel Honore had, over the past few weeks, been assessing the security needs of the Capitol in light of the attack.

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

The commission, she said, "would investigate and report on the facts and causes" of the attack; "the interference with the peaceful transfer of power"; and the "preparedness and response" of both the Capitol police and other branches of law enforcement.

She also said that, based on Lt. Gen. Honore's initial findings, Congress needed to allocate additional funding to "provide for the safety of members and the security of the Capitol".

Trump survived his second impeachment trial - the only president to face the process twice - on Saturday, after Democrat prosecutors failed to secure the two-thirds majority needed to convict him.

The vote split largely along party lines, with the seven Republicans joining the Senate's 48 Democrats and two independents in voting to convict.

The senior Republican in Congress, Senator Mitch McConnell, had voted against conviction on constitutional grounds, but after the vote declared Trump "responsible" for the assault on the Capitol.