WASHINGTON (AP) — White House officials took extraordinary steps to “lock down” information about President Donald Trump’s summertime phone call with the president of Ukraine, even moving the transcript to a secret computer system, a whistleblower alleges in a politically explosive complaint that accuses the administration of a wide-ranging cover-up.

The whistleblower, in a 9-page document released Thursday , provides substantial new details about the circumstances of the phone call in which Trump repeatedly spoke of how much the U.S. had aided Ukraine and encouraged new President Volodymyr Zelenskiy to help investigate political rival Joe Biden and his son.

Accusations of efforts to pressure the leader of a foreign nation to dig for dirt on a potential 2020 Trump rival are now at the heart of a House impeachment inquiry against the president. The whistleblower’s official complaint alleges a concerted White House effort to suppress the transcript of the call, and describes a shadow campaign of foreign policy efforts by the president’s personal lawyer Rudy Giuliani that unnerved some senior administration officials who felt he was circumventing normal channels.

“In the days following the phone call, I learned from multiple U.S. officials that senior White House officials had intervened to ‘lock down’ all the records of the phone call, especially the official word-for-word transcript of the call that was produced as is customary by the White House situation room,” the complaint says.

The previously secret document, with its detail and clear narrative, is likely to accelerate the impeachment process and put more pressure on Trump to rebut its core contentions and on his fellow Republicans to defend him or not. It also provides a road map for Democrats to seek corroborating witnesses and evidence , which will complicate the president’s efforts to characterize the findings as those of a lone partisan out to undermine him.

In response, Trump threatened “the person” who he said gave information to the whistleblower as he spoke at a private event in New York with staff from the U.S. mission to the United Nations.

“Who’s the person who gave the whistleblower the information? Because that’s close to a spy,” Trump said in audio posted by The Los Angeles Times. “You know what we used to do in the old days when we were smart? Right? The spies and treason, we used to handle it a little differently than we do now.”

On his Twitter account, Trump insisted the entire controversy is political: “The Democrats are trying to destroy the Republican Party and all that it stands for. Stick together, play their game and fight hard Republicans. Our country is at stake.” His tweet was in all capital letters.

Under pressure from House Democrats, the White House a day earlier released a rough transcript of the phone call between Trump and the Ukrainian president. In it, Trump prodded Zelenskiy to investigate former Vice President Joe Biden, a potential 2020 election foe, and Biden’s son Hunter, who was on the board of a Ukrainian gas company.

But the complaint released Thursday offered a broader picture of what was happening in the White House and the administration at the time. In the aftermath of the call, according to the whistleblower, White House lawyers were concerned “they had witnessed the president abuse his office for personal gain,” the complaint says.

The complaint has revived questions about the activities of Giuliani, who it says alarmed government officials by circumventing “national security decision making processes.” Giuliani, a Trump loyalist who represented the president in special counsel Robert Mueller’s Russia investigation, repeatedly communicated with advisers of Ukraine’s president in the days after the phone call.

The House intelligence committee released a redacted version of the whistleblower complaint Thursday ahead of testimony from Joseph Maguire, the acting director of national intelligence. Maguire acknowledged that the complaint alleged serious wrongdoing by the president but said it was not his role to judge whether the allegations were credible or not.

Maguire said he was unfamiliar with any other whistleblower complaint in American history that “touched on such complicated and sensitive issues.” He praised the whistleblower as having acted honorably, said he recognized the complaint as immediately sensitive and important and insisted the White House did not direct him to withhold it from Congress.

“I believe that everything in this matter here is totally unprecedented,” he said.

In the complaint, the anonymous whistleblower acknowledged not being present for Trump’s Ukraine call, but said multiple White House officials shared consistent details about it.

Adding another layer of intrigue, those officials told the whistleblower that “this was ‘not the first time’ under this administration that a presidential transcript was placed into this codeword-level system solely for the purpose of protecting politically sensitive — rather than national security sensitive — information,” the complaint said.

In this case, the complaint said, the officials told the whistleblower they were “directed” by White House lawyers to remove the electronic transcript from the computer system in which such transcripts are typically stored for coordination, finalization and distribution to Cabinet-level officials.

“This set of actions underscored to me that White House officials understood the gravity of what had transpired in the call,” the official complaint said.

“If this was all so innocent,” Senate Democratic leader Chuck Schumer of New York said in reaction, “why did so many officials in the White House, in the Justice Department and elsewhere make such large efforts to prevent it from being made public?”

The complaint also says multiple U.S. officials reported that Giuliani traveled to Madrid one week after the call to meet with one of Zelenskiy’s advisers, and that the meeting was characterized as a follow-up to the telephone conversation between the two leaders

House Speaker Nancy Pelosi, who endorsed an impeachment investigation in light of the Ukraine revelations, said the content of the complaint “lifts this into whole new terrain.”

The president, she said, “betrayed his oath of office, our national security and the integrity” of America’s elections.

Rep. Adam Schiff, the chairman of the House intelligence committee, said the whistleblower “has given us a road map” for the impeachment investigation.

In the Senate, which would hold a trial if the House voted to impeach Trump, there was an undercurrent of concern among Republicans.

Many Republicans declined comment about the complaint, saying at midday they had not read the whistleblower report. But a few mounted defenses of the president and attacked the whistleblower’s credibility.

Sen. Ron Johnson, R-Wis., who made several trips to meet with the Ukrainian president including the inauguration mentioned in the report, brushed off critics “impugning all kinds of nefarious motives here.”

“This has been blown way out of proportion,” Johnson said.