Former President Donald Trump has instructed his former aides not to comply with subpoenas from the special congressional committee investigating the Capitol riot, raising the prospect of the panel issuing criminal referrals for some of his closest advisers as early as Friday.

In a letter reviewed by The New York Times, Trump’s lawyer asked that witnesses not provide testimony or documents related to their “official” duties and instead to invoke any immunities they might have “to the fullest extent permitted by law.”

The House committee has ordered four former Trump administration officials — Mark Meadows, the White House chief of staff; Dan Scavino, a deputy chief of staff; Steve Bannon, an adviser; and Kash Patel, a Pentagon chief of staff — to sit for depositions and furnish documents and other materials relevant to its investigation. They all faced a Thursday deadline to respond.

Rep. Bennie Thompson, D-Miss., chair of the select committee, has threatened criminal referrals for witnesses who do not comply with the subpoenas, and said the committee expected witnesses “to cooperate fully with our probe.”

The move amounted to a declaration of war by Trump on the investigation and raised legal questions about how far the committee would be able to go in compelling information from a former president and his advisers.

The committee is demanding that Meadows and Patel submit to questioning next Thursday, and Bannon and Scavino the following day.

It is unclear whether President Joe Biden’s team will extend executive privilege — which shields a sitting president’s communications and deliberations from disclosure — to the former president.

The Justice Department and the White House have already waived executive privilege for a previous batch of witnesses who were asked to testify before the Senate Judiciary and House Oversight committees, which were investigating the Jan. 6 attack and the Trump administration’s efforts to subvert the results of the presidential election. The Justice Department argued that privilege was conferred in order to protect the institution of the presidency, not to provide immunity for wrongdoing.

Taylor Budowich, a spokesperson for Trump, said that the records request by the select committee was “outrageously broad” and that it lacked “both legal precedent and legislative merit.”

“Executive privilege will be defended, not just on behalf of President Trump and his administration, but also on behalf of the office of the president of the United States and the future of our nation,” he added.

The instructions from Trump were reported earlier by The Guardian.

The deadline for compliance from the select committee’s first batch of subpoenas came as it issued three more on Thursday, targeting organizers of the “Stop the Steal” rally that brought together many of Trump’s supporters who went on to violently storm the Capitol.

The latest subpoenas seek deposition testimony from Ali Abdul Akbar, also known as Ali Alexander, and Nathan Martin, both of whom were involved in organizing protests around the country — including in Washington on Jan. 6 — based on Trump’s lies that he was the rightful winner of the 2020 election and that it had been riddled with fraud. The committee also issued a subpoena for Stop the Steal LLC, an organization affiliated with the event.

“The rally on the Capitol grounds on Jan. 6, like the rally near the White House that day, immediately preceded the violent attack on the seat of our democracy,” Thompson said. “Over the course of that day, demonstrations escalated to violence and protesters became rioters.”

In the weeks before the attack, Alexander, a far-right activist and conspiracy theorist, made repeated reference during “Stop the Steal” events to the possible use of violence to achieve the organization’s goals, and he claimed to have been in communication with the White House and members of Congress regarding events planned to undermine the certification of the 2020 Electoral College results, the committee said.

Alexander has claimed that he, along with Reps. Mo Brooks of Alabama, Paul Gosar of Arizona and Andy Biggs of Arizona, all Republicans, set the events of Jan. 6 in motion.

“We four schemed up of putting maximum pressure on Congress while they were voting,” Alexander said in a since-deleted video posted online, “so that who we couldn’t lobby, we could change the hearts and the minds of Republicans who were in that body, hearing our loud roar from outside.”

Additionally, Alexander spoke at a rally on Jan. 5 held by the Eighty Percent Coalition at Freedom Plaza in Washington and led the crowd in a chant of “Victory or death,” the committee said.

The committee has issued 18 subpoenas, many focusing on the funding, planning and organization of the rally that morphed into a violent rampage at the Capitol, where Congress was meeting to formalize Biden’s election victory. Participants chanted “Hang Mike Pence,” threatened to shoot Speaker Nancy Pelosi and forced lawmakers to evacuate the building. About 140 police officers were injured, and several people died in connection with the riot.

The committee said it was trying to get to the bottom of the organizing of the Jan. 6 event, given the conflicting information its investigators have received.

An organization named One Nation Under God submitted a permit application in December to the U.S. Capitol Police for a rally about “the election fraud in the swing states” on Jan. 6 that listed Martin’s phone number and email address among the contact information.

But when a Capitol Police official spoke with Martin at the end of December, Martin claimed not to have any information about the rally and directed the official to speak with a vendor, the committee said. According to the police official, the vendor was “shocked” to learn this, because he was in “daily communication” with Martin about the event, the committee said.

After the Jan. 6 attack, Alexander released a statement acknowledging that Stop the Steal had obtained the rally permit “for our ‘One Nation Under God’ event,” the committee said. He said it was the intention of Stop the Steal to direct attendees of the rally to march to Lot 8 on the U.S. Capitol grounds, which is the location for which the Capitol Police granted the permit for the “One Nation Under God” rally. The permit application estimated the event would have only 50 attendees, not the hundreds who marched on the Capitol.

The subpoenas require Alexander and Martin to produce documents by Oct. 21 and testify at depositions next week.

The committee’s latest action came as the Senate Judiciary Committee released a lengthy interim report about Trump’s efforts to pressure the Justice Department to do his bidding in the chaotic final weeks of his presidency. Thompson said he planned to incorporate the Senate’s findings into the House inquiry.