Special counsel Robert Mueller has submitted his report on his Russia investigation to Attorney General Bill Barr.

In a letter sent to the chairs and ranking members of the House and Senate Judiciary Committees, Barr informed Congress the report was submitted on Friday and that Mueller had concluded his investigation.

Barr suggested in the letter that he might be in a position to brief Congress as soon as this weekend Mueller’s “principal conclusions.” The Justice Department is expecting those principal conclusions will become public.

Other information about Mueller’s findings could be provided to Congress after Barr consults with and Mueller and Deputy Attorney General Rod Rosenstein in compliance with Justice Department protocols, Barr wrote in the letter.

Barr said that there was no instance that Mueller was blocked by the Justice Department from taking an investigative action.

Mueller is not recommending any further indictments, multiple outlets reported. That includes any sealed indictments or indictments down the road, CNN reported.

White House Press Secretary Sarah Sanders said in a statement that White House had not received or been briefed on Mueller’s report.

“The next steps are up to Attorney General Barr, and we look forward to the process taking its course,” she said.

President Trump’s personal attorney Jay Sekulow said that, “We’re pleased that the Office of Special Counsel has delivered its report to the Attorney General pursuant to the regulations.”

“Attorney General Barr will determine the appropriate next steps,” Sekulow said in a statement.

The submission signals the winding down of a sprawling investigation that has resulted in more than three dozen people charged and at least five guilty pleas since Mueller was appointed in May 2017. The Russia investigation has also been subject of the President’s public and private ire, and a source of anxiety for the White House in the more than two years of its existence.

The submission of Mueller’s report, however, is only the beginning of what could be a high-stakes fight over what view — if any — the public will have into Mueller’s findings, which could speak to whether Trump or his campaign coordinated with Russia’s attack on the 2016 election or how aggressive the President’s attempts to obstruct the probe were.

It’s unclear just how expansive or comprehensive Mueller’s submission to Barr is. The special counsel regulations require only that he file a “confidential report explaining” his “prosecution or declination decisions.”

It is also unclear what Barr will do next with Mueller’s findings. The regulations mandate he inform Congress of any proposed moves by Mueller that were blocked by the attorney general, and they add that the “Attorney General may determine that public release of these reports would be in the public interest, to the extent that release would comply with applicable legal restrictions.”

In his confirmation testimony, Barr promised to be as transparent as possible but also said that he would comply with Justice Department rules and regulations, which discourage the public release of damaging information about individuals the Department declines to charge. That has raised fears that any criminal conduct Mueller has found Trump — whom DOJ policy says can’t be indicted while he’s president — will remain hidden from Congress or the public.

So far Mueller has spoken publicly only through court proceedings. In them, he has laid out an multi-layered Russian operation to influence the 2016 election, both through social media disinformation and through the hack and release of Democratic emails. That effort, his court filings say, was geared at boosting Trump to the detriment of Hillary Clinton.

Mueller has stopped short of accusing Trump or his allies of conspiring in this operation. However, his cases against Paul Manafort, Rick Gates, Michael Flynn, George Papadopoulos and Michael Cohen have laid out a pattern of lying and deception by Trump’s inner circle, including regarding their dealings with Russians and pro-Russian Ukrainians.

And while his court filings so far have not touched on Trump obstruction allegations, reporting on his team’s interviews with White House officials and others suggest a focus on Trump’s efforts to impede the federal investigation into Russia.

Mueller was appointed on May 17 2017, eight days after FBI Director James Comey was fired by Trump. Comey, about two months earlier, was pressured by Trump to drop an FBI investigation into Flynn, the former National Security Advisor who plead guilty in December 2017 to lying to the FBI about his conversations with a Russian official during the presidential transition.

Mueller’s investigation has reportedly included questioning of witnesses about Trump’s attempts to remove the special counsel, while seeking answers from Trump himself about his decision to fire Comey.

The charges against Manafort, Trump’s former campaign chairman, and Gates, Manafort’s longtime deputy who also worked on the campaign was the first major indictment Mueller unveiled in November. Those charges mainly focused on financial crimes stemming from the work they did in Ukraine prior to the 2016 campaign. However, on the same day, Mueller also unsealed a guilty plea from Papadopoulos, a former campaign advisor, who had lied to the FBI in January 2017 about his contacts with Russians during the 2016 campaign.

Meanwhile, Cohen, Trump’s longtime fixer who described himself as a lawyer for Trump Organization, plead guilty to November to lying to Congress about his work on a Trump Tower project in Moscow — work that continued well into the 2016 campaign, contradicting Trump’s own public comments about his Russian business dealings.

There a number of episodes raising allegations of Trump-Russia connections that Mueller has not addressed publicly. It is unknown what his investigation has turned up on a June 2016 meeting at Trump Tower between Russians and Manafort, Trump son Donald Jr, and Trump son-in-law Jared Kushner. It is unclear what he has found about a meeting Erik Prince, who informally advised the campaign, and Kremlin-aligned Russian oligarch in January 2017. There is also a cloud of mystery around interviews Mueller reportedly did concerning the influence Middle Eastern countries sought to curry with Trump’s circle .