WASHINGTON — “We are essentially in a national emergency,” Michael T. Flynn declared on Jan. 5, during an interview with the internet conspiracy theorist Alex Jones recorded in a luxurious suite at the Willard Intercontinental Hotel near the White House.
“The truth is going to come out,” said Mr. Flynn, the former three-star general and national security adviser. “Donald Trump will continue to be president of the United States for the next four years.”
In another room of the five-star hotel, a phalanx of lawyers and political advisers for Mr. Trump — including Rudolph W. Giuliani, his personal lawyer; Bernard B. Kerik, a former New York City police commissioner; and John Eastman, a scholar working feverishly on a legal strategy to prevent Joseph R. Biden Jr. from assuming the presidency — had set up a kind of command post. On the hotel’s grand front steps, Roger J. Stone Jr., a longtime Trump adviser, was flashing his signature Nixon victory sign to fans as members of the Oath Keepers, a militant group, protected him.
What unfolded at the Willard Hotel in the hours before the Capitol riot has become a prime focus of the House committee investigating the Jan. 6 attack as the panel intensifies its scrutiny into whether there was any coordination or tie between those pushing a legal strategy to overturn the election results and those who stormed the Capitol that day as Congress met to count the electoral votes to formalize Mr. Biden’s victory.
This week, the committee issued subpoenas to several of Mr. Trump’s advisers who gathered there — including Mr. Flynn, Mr. Eastman and Mr. Kerik — and communications with Mr. Giuliani and Mr. Stone are among the materials investigators have demanded from the former president, who is stonewalling the inquiry.
On Tuesday, the committee announced 10 new subpoenas that seemed to expand the aperture of the inquiry even further, seeking information from top officials in Mr. Trump’s White House including Stephen Miller, his senior adviser; Keith Kellogg, the national security adviser to Vice President Mike Pence; Johnny McEntee, the former president’s personnel chief; and others.
In the past two days alone, the panel has nearly doubled the number of subpoenas it has issued, bringing the total to 35.
In recent weeks, the committee has hired new investigators, pored over thousands of documents and heard privately from a stream of voluntary witnesses, from rally planners and former Trump officials to the rioters themselves.
More than 150 witnesses have been interviewed, some of whom surprised investigators by proactively contacting the committee to testify, according to two people familiar with the investigation who described the confidential inquiry on the condition of anonymity.
The panel has learned details about how “Stop the Steal” rally organizers used deception to obtain permits from the Capitol Police to hold rallies near the Capitol; how Mr. Trump and White House officials coordinated with organizers of the rally whose attendees would later storm the Capitol; and how deeply Mr. Trump’s chief of staff, Mark Meadows, was involved in pushing false claims of widespread election fraud.
Working out of a nondescript office building at the bottom of Capitol Hill, the committee’s investigators have divided themselves into color-coded teams to pursue several avenues of inquiry. They are looking into:
The money trail. Investigators are scrutinizing the groups that funded the protests that preceded the violence, which involved rioters from at least 44 states, and promoted and spread lies online that helped radicalize the crowd.
Planning meetings. The panel is pressing for answers about gatherings at the Willard and other Washington hotels where Mr. Trump’s allies who were involved in the effort to overturn the election, including Stephen K. Bannon, Mr. Giuliani and Mr. Eastman, met in the hours before the riot.
Foreknowledge of violence. The most difficult piece of the investigation involves unearthing evidence that Mr. Trump or anyone in his inner circle had foreknowledge that violence was a possibility on Jan. 6, and whether they took any steps to either encourage or discourage the storming of the Capitol. Mr. Bannon, whom the House voted to hold in criminal contempt of Congress for defying a subpoena from the committee, predicted on his podcast a day before the riot that “all hell is going to break loose tomorrow.”
The committee wants to question Mr. Bannon about his presence at a meeting at the Willard on Jan. 5, when plans were discussed to try to block Congress’s formalization of the election the next day.
“Mr. Bannon was in the war room at the Willard on Jan. 6,” Representative Liz Cheney, Republican of Wyoming and the vice chairwoman of the committee, said during a recent hearing.
Mr. Stone, who was photographed with Mr. Flynn on Jan. 5, has claimed that he had departed his room at the Willard to leave town as rioters stormed the Capitol, after he decided against a plan to “lead a march” from the White House Ellipse to the Capitol, according to video posted to social media.
But the Willard was only one hub of Trump activity before the Jan. 6 riot, when members of the former president’s inner circle also congregated at the nearby Trump International and other hotels to plan their bid to invalidate the election results.
Mr. Flynn was also present at the Trump International Hotel on Jan. 5 for a meeting that included about 15 people, where the discussion centered on “how to put pressure on more members of Congress to object to the Electoral College results,” according to one attendee, Charles Herbster, a Republican candidate for governor of Nebraska.
Among those in attendance, according to Mr. Herbster, were Mr. Trump’s sons Eric and Donald Jr.; Mr. Giuliani; Senator Tommy Tuberville of Alabama; the Trump advisers Peter Navarro, Corey Lewandowski and David Bossie; and Mike Lindell, the MyPillow executive and conspiracy theorist.
Unlike Mr. Bannon, many witnesses who have received subpoenas have begun complying with the committee to varying degrees.
“We have a great many people who are cooperating,” said Representative Adam B. Schiff, Democrat of California and a member of the committee. “We’re conducting interviews and depositions almost every day.”
But some who have agreed to talk are unlikely to help the committee find the evidence of a conspiracy that it is seeking. Mr. Kerik, for instance, said he was eager to present investigators with examples of election fraud he claimed to have uncovered.
He said he hoped to be “able to present the evidence that we obtained about voting irregularities so that government officials could follow up,” but became angry when the committee described him as being “involved in efforts to promote false claims of election fraud” and working to “promote baseless litigation.”
The committee has not yet sent a subpoena to any member of Congress, even those far-right Republicans who fanned the flames of conspiracy and anger with election falsehoods and incendiary rhetoric in the buildup to the riot.
The F.B.I. said in March that it had no evidence of communications between the rioters and members of Congress during the deadly attack.
“In terms of the evidence of member involvement, we’re still at a very early stage of our investigation,” Mr. Schiff said.
Tom Van Flein, the chief of staff to Representative Paul Gosar, Republican of Arizona, who was deeply involved in the “Stop the Steal” effort, said he had not yet been asked to come in for an interview, despite being named in a documents request from the committee.
Mr. Van Flein denied that either he or his boss was involved in planning for events on Jan. 6 beyond the objections in the House to Mr. Biden’s victory.
“Congressman Gosar and other members of Congress have and had every right to attend rallies and speeches,” Mr. Van Flein wrote in an email. “None of the members could have anticipated what occurred later.”
At the center of the investigation is Mr. Trump himself, who has sued in federal court to block the release of documents related to Jan. 6 and directed his associates to refuse to cooperate with the committee, citing executive privilege.
The latest round of subpoenas reflected the panel’s effort to ascertain the former president’s every move on the day of the riot. It is demanding testimony from Nicholas Luna, one of Mr. Trump’s “body men” who was in the Oval Office as the former president pressured Mr. Pence to refuse to certify the election.
Also summoned was Mr. McEntee, who was reportedly in the Oval Office during a meeting with Mr. Trump and Mr. Pence when Mr. Giuliani suggested seizing Dominion voting machines, and Kayleigh McEnany, the former White House press secretary who was reportedly with Mr. Trump at times as he watched the attack.
The committee also wants to hear from Ben Williamson, a top aide to Mr. Meadows who the committee asserted had tried unsuccessfully to get Mr. Trump to issue a statement on Jan. 6 condemning the violence at the Capitol. Christopher Liddell, a former deputy White House chief of staff who investigators said tried to resign on the day of the riot but was persuaded not to do so, was also subpoenaed.
In its order to Mr. Miller, the committee said that he had helped to spread false claims of voter fraud in the election, and to encourage state legislatures to appoint alternate slates of electors in an effort to invalidate Mr. Biden’s victory.
Those scheduled to receive a subpoena on Tuesday either did not respond to a request for comment or could not be reached.