An internal investigation by the US Capitol police (USCP) has recommended disciplinary measures against six of its officers for their actions during the 6 January riot, although none will face criminal charges.

In a statement, the USCP said its office of professional responsibility had opened 38 separate investigations following the deadly attack on the Capitol by supporters of Donald Trump seeking to overturn his election defeat.

Investigators were able to identify officers involved in 26 of the cases, the statement said, and found no evidence of wrongdoing in 20.

Of the other six, it said, three are cited for conduct unbecoming, one for failing to comply with directives, one for improper remarks, and one for “improper dissemination of information”.

None of the officers was named, and no specific details of the incidents were released because “internal investigations, including any recommended disciplinary actions, as well as personnel matters are not public information”, the department said, adding that the US attorney’s office did not find evidence that any of its officers had committed a crime.

“The six sustained cases should not diminish the heroic efforts of the United States Capitol police officers. On January 6, the bravery and courage exhibited by the vast majority of our employees was inspiring,” the statement concluded.

The disciplinary actions were first reported by CNN, which noted in February that the USCP had suspended six officers with pay and was investigating 29 more. It is unclear if the suspended officers were the ones now facing disciplinary action.

USCP spokesperson John Stolnis said that the acting chief of the Capitol police, Yogananda Pittman, was committed to pursuing disciplinary action against “any member of her department whose behavior is not in keeping with the department’s rules of conduct”.

One officer was seen taking selfies with members of the mob, while another was photographed in Trump’s trademark Make America Great Again (Maga) baseball cap, according to anecdotal evidence at the time.

Separately, a House select committee is investigating the attack on the Capitol building, which followed Trump’s urging of his supporters to “fight like hell” in support of false claims from the former president that the election was stolen from him.

Michael Fanone, a USCP officer beaten and Tasered during the insurrection, testified to the committee in July that he “went to hell and back”, as he and colleagues defended the Capitol from the rioters, and had subsequently received vulgar voicemails and death threats for speaking out.

Others have filed lawsuits against Trump, holding him responsible for the injuries they sustained. One USCP officer suffered a stroke and died following the violence, and four others have since died by suicide.