The whistleblower complaint at the heart of a weeks-long standoff between the White House and Congress that led to a formal impeachment inquiry was finally made available to lawmakers on Wednesday. And Democrats who read it said it contained important new information, even though they couldn't discuss what it was.

The document by the still-unidentified whistleblower contained allegations that were "very credible" and "deeply disturbing," said House Intelligence Committee Chairman Rep. Adam Schiff, D.-Calif. The complaint is believed to be related to a July phone call between President Donald Trump and Ukrainian President Volodymyr Zelenskiy.

"The complaint is very well written, and certainly provides information for the committee to follow up with other witnesses and documents," Schiff, who was among the lawmakers permitted to view the classified complaint, said.

The complaint was filed last month by the acting inspector general for Director of National Intelligence, who found it to be "credible" and "urgent." It was supposed to be turned over to Congress within a week, but the acting Director of National Intelligence, Joseph Maguire, refused to do so on the advice of the Justice Department.

"I think it's a travesty that this complaint was withheld as long as it was because it was an urgent matter and it is an urgent matter, and there was simply no basis to keep this from the committee," Schiff said.

"The idea that the Department of Justice would have intervened to prevent it from getting to Congress throws the leadership of the that department into further ill repute," Schiff said.

Sen. Ben Sasse, R-Neb., said there are "really troubling things here."

“Republicans ought not to be rushing to circle the wagons to say there’s no there there when there’s obviously lots that’s very troubling there," Sasse, a former Trump critic who was recently endorsed by the president, told reporters. He also chided Democrats "for using words like impeachment."

"Everybody in this whole process should slow down," he said.

He and other lawmakers from the intelligence committees were allowed to review the document in a secure location in the Capitol, as was Congressional leadership.

Senate Minority Leader Chuck Schumer, D-N.Y., told reporters that “having read the documents in there I’m even more worried about what happened than I was when I read the memorandum of the conversation. There are so many facts have to be examined."

"It’s very troubling," he added in a statement a short time later. “The public has a right to read the whistleblower’s complaint for themselves. The contents of the complaint should be made public immediately."

Rep. Elise Stefanik, R-N.Y., also called for the document to be made public.

"I do not support impeachment of President Trump," she tweeted after reviewing the complaint, but "I believe strongly in transparency and it should be immediately declassified and made public for the American people to read."

The document was made available hours after text of the July phone call was released. Maguire is scheduled to testify about the dispute in appearances before the House and Senate on Thursday.

Sen. Roy Blunt, R-Mo., said his level of concern was "no higher than it was before I read the complaint."

“I want to sort out the different views of what I read before I decide whether I’m concerned with what I read or not,” he said.

Rep. Joaquín Castro, D-Texas, and Rep. Jackie Speier, a Democrat from California, had different takeaways.

"Just read the Whistleblower report," Castro tweeted. "This thing is bigger that I thought."

"I can describe that complaint as nothing short of explosive," Speier said on MSNBC Wednesday night.

CORRECTION (Sept. 25, 2019, 10:30 p.m. ET): An earlier version of this article misspelled the first name of a congressman from Texas. He is Joaquín Castro, not Joauquin.