The office of the director of national intelligence gave lawmakers access to a whistleblower complaint that includes President Trump's conversation with the Ukrainian president on Wednesday, hours after the White House released a memorandum summarizing the call between the two leaders. After seeing the complaint, one Democratic congresswoman described it as "nothing short of explosive."

The complaint precipitated House Speaker Nancy Pelosi's decision to announce a formal impeachment inquiry on Tuesday.

The administration's decision to give lawmakers the document came one day after the Senate voted unanimously on a resolution demanding the material. The House was set to vote on its own resolution on Thursday before the committees were given the document.

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Senate Intelligence Committee Chairman Richard Burr told reporters his committee had received the whistleblower complaint shortly after 4 p.m. Members of the House and Senate Intelligence Committees and party leaders streamed in and out of a secure hearing room on Capitol Hill late Thursday afternoon to examine the document, which one lawmaker said was 10 to 12 pages long.

In a quick statement after viewing the report, House Intelligence Committee Chairman Adam Schiff said: "I want to thank the whistleblower for coming forward."

"I found the allegations deeply disturbing and very credible. I can understand why the inspector general found them credible," Schiff said.

Democratic Congressman Mike Quigley told reporters the complaint "reinforces our concerns," and called it "disturbing" and "alarming."

Representative Jackie Speier, a California Democrat, in November 2017 Yuri Gripas / REUTERS

Democratic Representative Jackie Speier, of California, said on MSNBC Wednesday night that the complaint is "nothing short of explosive. It is so much more than the summary of the telephone call that has been presented by the White House as evidence. I am not even in a position to say that that was involved in the complaint until it is actually declassified. I can tell you that I was stunned by the breadth of the complaint and the details (with) which the whistleblower expressed his concerns."

The Associated Press says most Republicans stuck up for the president or were quiet as they left the secure rooms.

Senate Intelligence Committee member Ben Sasse, of Nebraska, said, "This is going to take a lot of time but there's obviously some really troubling things here."

He criticized Republicans he said are rushing to defend the administration and Democrats he said are rushing to impeach the president.

The complaint involves the call between Mr. Trump and Ukrainian President Volodymyr Zelensky on July 25, during which Mr. Trump asked Zelensky to investigate former Vice President Joe Biden and his son, Hunter Biden. The call came days after the Trump administration froze nearly $400 million in aid to Ukraine.

The complaint was submitted to the inspector general for the intelligence community, who found it to be of "urgent concern." However, the Justice Department, which said that the complaint involved a possible campaign finance violation, reviewed the record of the call and determined that there had been no wrongdoing and concluded that "no further action was warranted," according to spokesperson Kerri Kupec.

The White House released a document summarizing the call earlier on Wednesday, which revealed that the president had urged Zelensky to probe Biden and Hunter Biden, who sat on the board of a Ukrainian natural gas company.

The president met with Zelensky in New York on Wednesday, where he is attending the opening of the United Nations General Assembly.

"I think you read everything. I think you read text," the Ukrainian leader said, when asked whether he felt pressured to investigate the Bidens. "I'm sorry, but I don't want to be involved [in] democratic, open elections of USA. We had, I think, good phone call. It was normal."

According to the memo, Zelensky said Ukraine was "almost ready to buy more Javelins from the United States for defense purposes," referring to powerful anti-tank missiles. Mr. Trump responded he "would like you to do us a favor though," telling Zelensky he would like to find out what happened with "this whole situation with Ukraine." Mr. Trump also mentioned CrowdStrike, a cybersecurity company that helped investigate Russian interference in the 2016 election.

Mr. Trump later mentioned "the other thing," saying "there's a lot of talk about Biden's son." Zelensky pledged that a new prosecutor would look into the case and asked for additional information. Mr. Trump told Zelensky he would have Giuliani and Attorney General William Barr call. The Justice Department, which released the memo of the call, said Wednesday that Barr never discussed anything related to Ukraine with Giuliani.

On Wednesday, Democrats said the memo was worse than they anticipated, with Schiff saying it was reminiscent of a "classic mafia-like shakedown." But Mr. Trump claimed that the document vindicated him and said that the memo showed no explicit quid pro quo with Ukraine.

Joseph Maguire, the acting director of national intelligence, will testify before the House Intelligence Committee on Thursday. He disputed a report by The Washington Post that he had threatened to resign if the White House tried to block him from talking about the complaint before Congress. "I have never quit anything in my life, and I am not going to start now," he said in a statement.

The whistleblower also wants to testify before the committee, according to Schiff.

Stefan Becket, Kathryn Watson and Emily Tillett contributed to this report