The U.S. House of Representatives select committee investigating the events of Jan. 6 issued subpoenas on Thursday to former White House Chief of Staff Mark Meadows and three other allies of former President Donald Trump.

These are the first subpoenas announced by the committee and represent its intensifying interest in what transpired in the White House before and during the assault on the Capitol. Demands for documents and depositions were also sent to former Deputy Chief of Staff Dan Scavino, former Pentagon Chief of Staff Kash Patel and former Trump adviser Steve Bannon.

The committee’s letter to Meadows cited a June ProPublica report, which found that he was involved in shaping the rally that preceded the attack on the Capitol and presented evidence that organizers may have warned him about the dangers of an unpermitted march. The letter also cited emails Meadows sent to top Justice Department officials in the weeks before Jan. 6, asking the officials to investigate fringe theories pertaining to the 2020 election.

“The investigation has revealed credible evidence of your involvement in events within the scope of the Select Committee’s inquiry. You were the President’s Chief of Staff and have critical information regarding many elements of our inquiry,” said the letter to Meadows, written by the committee chairman, Rep. Bennie Thompson, D-Miss.

ProPublica’s reporting described senior Trump officials’ efforts to contain an increasingly volatile situation in the days and hours before the Jan. 6 attack on the Capitol and added new details suggesting aides knew the day could turn chaotic.

The reporting also raised questions as to whether Meadows specifically was warned about the potential danger of an unpermitted march on the Capitol from the White House Ellipse, which had been announced days before Jan. 6 by far-right provocateur Ali Alexander.

Rally organizers Dustin Stockton and Amy Kremer feared that the march could present a legal liability and a public safety risk, according to Stockton and others. Stockton told ProPublica that he and Kremer sought to push top White House officials to address the concerns over the march.

He said he and Kremer agreed she would take the matter directly to Meadows. Shortly afterward, she told Stockton “the White House would take care of it,” which he interpreted to mean she had contacted top officials about the march.

Kremer denied ever speaking to Meadows or any other White House official about her concerns going into Jan. 6. But in a Dec. 27 text from Kremer obtained by ProPublica, she told her fellow organizers that “​​the WH and team Trump are aware of the situation” with Alexander and that she needed “to be the one to handle both.”

Through his adviser, Ben Williamson, Meadows declined to answer questions for our original story. Meadows and Williamson did not immediately respond to a request for comment on the subpoena.

The full picture of what Meadows and the other officials knew remains unclear, but the committee has asked that the Trump allies provide documents by Oct. 7 and appear for depositions the following week.