The House select committee investigating the Capitol attack on Tuesday issued subpoenas to the leaders of the far-right Proud Boys and Oath Keepers militia, directly focusing for the first time on the instigators of the violence at the 6 January insurrection.

The subpoenas demanding documents and testimony targeted both the leaders of the paramilitary groups on the day of the Capitol attack that sought to stop the certification of Joe Biden’s election win, as well as the organizations behind the groups.

House investigators in total issued five subpoenas to Proud Boys International LLC and its chairman, Henry “Enrqiue” Tarrio, the Oath Keepers group and its president, Stewart Rhodes, as well as Robert Patrick Lewis, the chairman of the 1st Amendment Praetorian militia.

The chair of the select committee, Bennie Thompson, said in a statement that subpoenas reflected the panel’s interest in uncovering potential connections between the paramilitary groups, efforts to subvert the results of the 2020 election and the Capitol attack.

“We believe the individuals and organizations we subpoenaed today have relevant information about how violence erupted at the Capitol and the preparation leading up to this violent attack,” Thompson said.

Dozens of paramilitary group members have been indicted by the justice department as they pursue criminal charges against rioters involved in the insurrection, but the select committee had not yet publicly sought their cooperation in its investigation.

The new subpoenas are aimed to uncover whether there was any coordination between the paramilitary groups and the White House, according to a source close to the investigation, and whether Donald Trump had advance knowledge of plans about the Capitol attack.

The select committee said they subpoenaed the Proud Boys group since its members called for violence leading up to 6 January and that at least 34 individuals affiliated with the group had been indicted by the justice department for their roles in storming the Capitol.

Thompson suggested in the subpoena letters to Proud Boys International LLC and Tarrio that the group appeared to have advance knowledge of the violent nature of the Capitol attack, having fundraised for “protective gear and communications” in planning for 6 January.

The select committee said they similarly subpoenaed the Oath Keepers for their part in leading the deadly assault on Congress, which a federal grand jury indictment in Washington DC described as a conspiracy involving at least 18 members.

The members of the Oath Keepers led by Rhodes, the select committee said, planned their assault on the Capitol in advance, and travelled to Washington DC with paramilitary gear, firearms, tactical vests with plates, helmets and radio equipment.

According to the indictment, the main unnamed conspirator – believed to be Rhodes – was in direct contact with his Oath Keepers members before, during, and shortly after the Capitol attack, the select committee added in the subpoena letters.

The justice department has said Rhodes directed members of the Oath Keepers as they stormed the Capitol on 6 January but has not been charged with a crime and has denied any wrongdoing. He surrendered his phone to law enforcement and has sat for an interview with the FBI.

House investigators also subpoenaed the leader of the 1st Amendment Praetorian, as Lewis was in constant contact with Trump operatives based at the Willard hotel in Washington DC that served as a “command center” for Trump to stop Biden’s certification.

The select committee said to Lewis that he was subpoenaed in part because he claimed the day after the Capitol attack that he “war-gamed” with constitutional scholars about how to stop Biden from being certified president on 6 January.

Thompson noted in the subpoena letter that members of the 1st Amendment Praetorian wore body cameras, suggesting the select committee’s interest in obtaining those recordings.

The five subpoenas come a day after House investigators issued subpoenas to several Trump operatives including Roger Stone and Alex Jones. The select committee demanded documents from the groups by 7 December, and testimony from its leaders later in the month.