WASHINGTON — Special Counsel Robert Mueller delivered a report on his investigation into Russian interference in the 2016 election to Attorney General William Barr, after a weeks-long waiting game for word that Mueller’s probe was reaching its conclusion.

The details of the report are still confidential after a nearly two-year investigation that had led to dozens of indictments and has captivated the attention of the media and the public. A Justice Department official told multiple news outlets that Mueller is recommending no new charges.

President Trump has insisted that there was “no collusion” between his campaign and Russian interests, words that he repeated often as he relentlessly attacked Mueller’s work as politically motivated and a judicial overreach.

Reporters staked out Mueller’s office in recent days and others were at the Justice Department, watching for any signs. Mueller’s team has been notoriously mum on offering any public details of what the report says or even when it would be completed.

The news came at about 5 p.m. ET that the report had been delivered, and Barr also informed Congress in a letter that the investigation was finished. Broadcast networks broke in for special reports, and cable news networks provided coverage throughout the day and planned to focus on the story through the evening.

In a letter to leaders of the House and Senate Judiciary committees, Barr wrote that there were “no instances” of Mueller’s proposed action by his team that were “inappropriate or unwarranted.” He wrote that he was reviewing the report to determine what could be shared with the public and the committee.

“I remain committed to as much transparency as possible, and I will keep you informed as to the status of my review,” Barr wrote.

He said “principle conclusions” from Mueller’s report may be shared with members of Congress “as soon as this weekend.”

Mueller began his investigation in May, 2017, after he was appointed special counsel after Trump fired the FBI director, James Comey. Mueller, a former FBI director himself, remained an elusive public figure throughout the process, never giving any interviews and showing the progress of his work only as he issued indictments.

Those included a series of figures close to Trump, including his former national security adviser, Michael Flynn; his former campaign chairman, Paul Manafort; his former personal attorney, Michael Cohen; and a former close associate, Roger Stone. In all, Mueller’s investigation yielded 38 indictments or pleas.

But the White House has insisted throughout that the President would not be implicated and, in Trump’s words, that the investigation was a “witch hunt.”

Very quickly after the report was delivered, Democrats and some Republicans called for its public release.

“The Special Counsel’s report must be provided to Congress immediately, and the Attorney General should swiftly prepare a declassified version of the report for the public,” said Sen. Mark Warner (D-Va.), the ranking member of the Senate Intelligence Committee. “Nothing short of that will suffice.”

Rep. Doug Collins (R-Ga.), the ranking member of the House Judiciary Committee, said he expects “the Justice Department to release the special counsel’s report to this committee and to the public without delay and to the maximum extent permitted by law.”

White House Press Secretary Sarah Huckabee Sanders said, “The next steps are up to Attorney General Barr, and we look forward to the process taking its course. The White House has not received or been briefed on the Special Counsel’s report.”

Some of the key questions are what Mueller will conclude about whether members of the Trump campaign engaged in any form of collusion with Russian sources, given reports of extensive contacts during the election with figures linked to Vladimir Putin. Also, he has reportedly examined whether Trump himself attempted to obstruct the investigation, including in comments made to Comey when he was still serving in his post.

In a joint statement, House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer also said the report should be made public, but warned of White House interference.

They said Barr “must not give President Trump, his lawyers or his staff any ‘sneak preview’ of Special Counsel Mueller’s findings or evidence, and the White House must not be allowed to interfere in decisions about what parts of those findings or evidence are made public.”

Even if Mueller clears Trump and other members of his circle, that is far from the end of investigations into his presidency, his personal finances and business interests, and other aspects of his life. House Democrats issued letters this month requesting information from 81 figures linked to Trump on a wide range of topics.

Mueller also referred investigations to other federal prosecutors, including those in New York who brought criminal charges against Cohen. But prosecutors there are still investigating other matters, including the finances surrounding Trump’s inaugural committee. Cohen also referred to additional criminal investigations when he testified before the House Oversight Committee earlier this month.