Five people, including a Capitol Police officer, died in the violence when throngs of former president Donald Trump's supporters attacked the Capitol, overpowering security forces.

Two law enforcement officers later committed suicide.

"Acting Chief Yogananda Pittman has directed that any member of her department whose behaviour is not in keeping with the department's rules of conduct will face appropriate discipline," police department spokesman John Stolnis said on Friday.

A US House of Representatives panel has scheduled a hearing on February 25 to look into Capitol security failures on January 6.

Just days after the attack, it was disclosed that two officers had been suspended. One had taken a selfie with a protester, while another wore a Trump-supporting hat and was directing protesters around the building.

It was unclear whether the two were among the 35 now being investigated or whether they were trying to quell the crowd by establishing personal contact with rioters.

The right-wing protesters went to Capitol Hill shortly after Trump addressed a crowd near the White House, telling them: "We fight. We fight like hell. And if you don't fight like hell, you're not going to have a country any more."

The rioters went to the seat of the US Congress, temporarily blocking lawmakers from formally certifying Joe Biden's victory in the November 3, 2020, presidential election, following repeated attempts by Trump to reverse that outcome.

One week after the riot, the Democratic-controlled House of Representatives impeached Trump on a charge of inciting an insurrection. The Senate failed to convict him when most Republicans voted for an acquittal.

Australian Associated Press