The US House of Representatives Select Committee investigating the January 6 Capitol attack sent subpoenas to four of Former President Trump’s closest advisors on Thursday.

“The Committee is investigating the facts, circumstances, and causes of the January 6th attack and issues relating to the peaceful transfer of power, to identify and evaluate lessons learned and to recommend corrective laws, policies, procedures rules, or regulations,” wrote Chairman Thompson, underscoring the committee’s authority established by House Resolution 503.

The subpoenas are part of the committee’s effort to gain information about Trump’s actions leading up to and during the January 6 riot. The subpoenas were sent to former White House Chief of Staff Mark Meadows, former White House Deputy Chief of Staff for Communications Daniel Scavino, former Defense Department official Kashyap Patel, and former Trump advisor Stephen Bannon.

Meadows was involved in efforts to overturn the results of the 2020 election and allegedly communicated with organizers of the January 6 rally. Scavino was with Trump on January 5 during a discussion on how to persuade Members of Congress not to certify Biden’s election win and promoted the January 6 event on Twitter. Patel was involved with discussions before and on January 6 regarding security at the Capitol with senior Pentagon officials. Bannon reportedly urged Trump on December 30, 2020 to focus his efforts on January 6, and he attended a gathering on January 5 as part of an effort to convince members of Congress not to certify Biden’s election win.

The four men must turn over documents by October 7. Patel and Bannon are requested to appear before the committee on October 14. Meadows and Scavino are requested to testify on October 15.

The committee is expected to authorize additional subpoenas and interview witnesses.