The committee has interviewed more than 475 witnesses and issued more than 100 subpoenas, including broad ones to banks as well as telecommunications and social media companies. Some of the subpoenas have swept up the personal data of Trump family members and allies, local politicians and at least one member of Congress, Representative Jim Jordan, Republican of Ohio. Though no subpoena has been issued for Mr. Jordan, his text messages and calls have shown up in communications with Mark Meadows, the former White House chief of staff, and in a call with Mr. Trump on the morning of Jan. 6, 2021.

Armed with reams of telephone records and metadata, the committee has used link analysis, a data mapping technique that former F.B.I. agents say was key to identifying terrorist networks in the years after the Sept. 11 attacks. The F.B.I. said it used a similar tactic last month to identify the seller of a gun to a man in Texas who took hostages at a synagogue.

Faced with at least 16 Trump allies who have signaled they will not fully cooperate with the committee, investigators have taken a page out of organized crime prosecutions and quietly turned at least six lower-level Trump staff members into witnesses who have provided information about their bosses’ activities.