A US judge has ruled a congressional committee investigating the Capitol riot can access some of ex-President Donald Trump’s White House records.
Mr Trump had argued the materials were covered by executive privilege, which protects the confidentiality of some White House communications.
The inquiry is trying to find out if Mr Trump had foreknowledge of the riot.
The ruling came on the day 10 Trump aides were issued with legal summonses to testify before lawmakers.
Hundreds of Mr Trump’s supporters stormed the Capitol building and disrupted the official certification of President Joe Biden’s election victory on 6 January this year.
The House of Representatives Select Committee wants to see a trove of phone records, visitor logs and other White House documents that could shed some light on the events leading up to the attack on Congress.
But US District Judge Tanya Chutkan ruled on Tuesday that the National Archives, the federal agency that holds Mr Trump’s White House records, should comply with the panel’s request.
Judge Chutkan, an Obama appointee, ruled that Mr Trump’s request for a preliminary injunction seemed to rest “on the notion that his executive power ‘exists in perpetuity'”.
“But Presidents are not kings, and Plaintiff is not President,” she added in the 39-page decision. The legal battle is likely to wind up at the Supreme Court.
Sixteen of Mr Trump’s closest aides have been subpoenaed in the past two days.
They include Kayleigh McEnany, the White House press secretary, Stephen Miller, who was Mr Trump’s senior adviser, Bill Stepien, campaign manager, Mark Meadows, former White House chief of staff, and Michael Flynn, former national security adviser.
The committee expects the witnesses to “comply fully”, he added.
The panel has already subpoenaed Dan Scavino, former deputy chief of staff, and Steve Bannon, a former Trump strategist.
Mr Bannon refused to comply with the subpoena and was charged with contempt of Congress.
Following the Capitol riot, Mr Trump was impeached by Congress, but cleared by lawmakers of inciting an insurrection. More than 670 people have been arrested for the invasion of the Capitol complex.