Members of special counsel Robert S. Mueller III’s team have told associates they are frustrated with the limited information Attorney General William P. Barr has provided about their nearly two-year investigation into Russian interference in the 2016 election and whether President Trump sought to obstruct justice, according to people familiar with the matter.

The displeasure among some who worked on the closely held inquiry has quietly begun to surface in the days since Barr released a four-page letter to Congress on March 24 describing what he said were the principal conclusions of Mueller’s still-confidential, 400-page report.

In his letter, Barr said that the special counsel did not establish a conspiracy between the Trump campaign and Russia. And he said that Mueller did not reach a conclusion “one way or the other” as to whether Trump’s conduct in office constituted obstruction of justice.

Absent that, Barr told lawmakers that he concluded the evidence was not sufficient to prove that the president obstructed justice.

But members of Mueller’s team have complained to close associates that the evidence they gathered on obstruction was alarming and significant.

“It was much more acute than Barr suggested,” said one person, who, like others, spoke on the condition of anonymity because of the subject’s sensitivity.

The New York Times first reported that some special counsel investigators feel that Barr did not adequately portray their findings.

Some members of the office were particularly disappointed that Barr did not release summary information the special counsel team had prepared, according to two people familiar with their reactions.

“There was immediate displeasure from the team when they saw how the attorney general had characterized their work instead,” according to one U.S. official briefed on the matter.

Summaries were prepared for different sections of the report, with a view that they could be made public, the official said.

The report was prepared “so that the front matter from each section could have been released immediately — or very quickly,” the official said. “It was done in a way that minimum redactions, if any, would have been necessary, and the work would have spoken for itself.”

Mueller’s team assumed the information was going to be made available to the public, the official said, “and so they prepared their summaries to be shared in their own words — and not in the attorney general’s summary of their work, as turned out to be the case.”

Another person familiar with the matter disputed that characterization, saying the summaries contained sensitive information that will likely require redaction.

Justice Department spokeswoman Kerri Kupec said in a statement Thursday that every page of Mueller’s confidential report was marked with a notation that it may contain confidential grand jury material, adding that it “therefore could not be publicly released.”

“Given the extraordinary public interest in the matter, the Attorney General decided to release the report’s bottom-line findings and his conclusions immediately — without attempting to summarize the report — with the understanding that the report itself would be released after the redaction process,” she said. “As the Attorney General stated in his March 29th letter to [Senate Judiciary Committee Chairman Lindsey O. Graham (R-S.C.) and House Judiciary Committee Chairman Jerrold Nadler (D-N.Y.)], he does not believe the report should be released in ‘serial or piecemeal fashion.’ The Department continues to work with the Special Counsel on appropriate redactions to the report so that it can be released to the Congress and the public.”

A spokesman for the special counsel did not immediately respond to a request for comment.

Trump attorney Rudolph W. Giuliani said the frustrations on Mueller’s team were coming from “disgruntled” staffers.

In an interview Wednesday night with Fox News host Laura Ingraham, Giuliani said the reports prove the special counsel’s office was biased.

“They are a bunch of sneaky, unethical leakers,” he said. “And they are rabid Democrats who hate the president of United States.”

Giuliani added, “I am absolutely confident that the report will bear out the conclusions. The conclusions: no obstruction, no Russian collusion of any kind. It will bear that out.”

In the wake of the limited information released by Barr, Trump declared that the Mueller report provided him with “complete and total exoneration.” He has repeatedly called for an inquiry into how the investigation began in the first place.

“There was no collusion with Russia,” Trump said. “There was no obstruction.”

During nearly two years of work, Mueller’s team — which included 19 lawyers and roughly 40 FBI agents, analysts and other professional staff — worked in near silence, speaking only rarely, through public documents filed in court. The fact that some have been confiding in recent days to associates is a sign of the level of their distress.

Some members of Mueller’s team appear caught off guard by how thoroughly the president has used Barr’s letter to claim total victory, as the limited information about their work has been weaponized in the country’s highly polarized political environment, according to people familiar with their responses.

Their frustrations come as polls show many Americans have already drawn conclusions about the special counsel findings — even though only a handful of words from the report have so far been released.

On Wednesday night, Rep. Adam B. Schiff (D-Calif.), chairman of the House Intelligence Committee, questioned why Barr did not release the special counsel’s summary material.

“It’s been my assumption that a 400-page report has an executive summary already, and so of course it begged the question, ‘Why did Barr feel the need to release his own summary?’ ” he said on MSNBC. “Why didn’t he release a summary produced by Bob Mueller itself instead of trying to shape it through his own words?”

It is not yet clear if Mueller’s full investigative findings will be released publicly.

Barr told Congress in a letter last week that the principal conclusions he described were not meant to be a summary of Mueller’s investigation. He said he is aiming to submit a redacted version of the report to Congress by mid-April after removing classified and grand jury material, as well damaging information about peripheral players who were not charged with crimes.

“Everyone will soon be able to read it on their own,” Barr wrote.

The House Judiciary Committee voted on Wednesday to authorize a subpoena for the entire report, as well as investigative materials, though Nadler said he will wait to issue the demand until he sees what Barr makes public. Some Democrats have also indicated they wish to see Mueller testify to Congress, which would allow lawmakers to question him about Barr’s letter.

Barr said the special counsel’s report is divided into two parts. The first pertains to the Russian effort to influence the 2016 election and documents crimes committed by Russians in that regard. The second addresses a number of actions by the president as potentially raising concerns about obstruction of justice, Barr said.

He said that the special counsel’s decision not to reach a legal conclusion on obstruction left it to him to determine whether Trump’s conduct as described constituted a crime.

Deputy Attorney General Rod J. Rosenstein “and I have concluded that the evidence developed . . . is not sufficient to establish” that the president committed obstruction of justice, he wrote in his letter to Congress.

Democrats have questioned Barr’s conclusion, noting that he wrote a 2018 memo that criticized Mueller’s obstruction inquiry and argued that the president cannot be accused of obstruction for exercising his broad constitutional powers.

Devlin Barrett and Philip Rucker contributed to this report.