(CNN) The Justice Department probe into the origins of the Russia investigation is continuing to progress as the coronavirus pandemic shuts down institutions across the country, Attorney General William Barr said this week.

Still, department officials say the pandemic is having an effect, and Barr's initial expectation that the probe would be completed by May or June could be delayed.

That could push the presentation of any findings from John Durham , the Connecticut prosecutor whom Barr appointed last year to review the investigation, closer to the November presidential election. A delay could also push the investigation so close to the election that releasing the findings would violate Justice Department guidelines regarding actions by prosecutors that could have an impact on an election.

Barr said he saw no reason for those rules to come into play since no one being investigated is running for office. His comments came in a radio interview with conservative host Hugh Hewitt that aired Tuesday.

"You don't indict candidates or perhaps someone that's sufficiently close to a candidate, that it's essentially the same, you know, within a certain number of days before an election. But you know, as I say, I don't think any of the people whose actions are under review by Durham fall into that category," Barr said.

But while Barr hasn't explained further developments in Durham's investigation, the incremental developments have become political fodder for Trump and other conservatives who still seek to discredit the Russia probe and special counsel Robert Mueller's findings.

Amid the pandemic, Durham and a team of prosecutors and investigators have continued their work, even requesting witness information after the country largely shut down in March because of coronavirus restrictions, according to people briefed on the investigation. Leading up to the lockdown, Durham's team had spent many days a month reviewing classified intelligence inside a special facility for reviewing classified documents known as a SCIF.

In recent weeks Durham has added to his team of investigators who operate in Connecticut and Washington, DC, including FBI agents and the chief of the violent crimes and narcotics section in the US Attorney's Office in Washington, Anthony Scarpelli, people familiar with the probe said.

The Justice Department declined to comment on the state of the probe. Barr has occasionally touted what he says is the severity of Durham's findings, but the department has said very little about the makeup of Durham's team.

Durham's focus appears to have turned toward decisions made by top officials overseeing the intelligence analysis of Russian election interference efforts in 2016, and particularly the leadership of then-CIA director John Brennan and then-Director of National Intelligence James Clapper, according to more than a half dozen people familiar with the investigation.

Durham's investigators have asked witnesses about examining the information that backs the US intelligence community's assessment that the Russian interference effort was aimed in part to get Donald Trump elected, a person familiar with the matter said.

That finding is one that has particularly irritated Trump, who has lashed out publicly about it. But even the latest extensive review of the investigation, by the Senate Intelligence Committee this week, found that Russia was trying to help Trump in 2016 and the intelligence community's conclusions during the Obama administration on Russian interference came without political bias.

CNN previously has reported that Durham is investigating the actions of a lower-level FBI attorney who included incorrect information in a surveillance application in 2016.

The Durham review also has included looking at the information the intelligence community had to back up an FBI court application to wiretap former Trump campaign adviser Carter Page.

Barr and the President have openly doubted whether the FBI even had reason to open a full Investigation of the Trump campaign and Page -- even after Justice Department watchdog Michael Horowitz reviewed the FBI's Russia investigation. Horowitz, who worked independently from Justice, found it properly predicated but noted errors in the FBI's work.

Mueller, in his own two-year investigation of 2016, found extensive evidence of Russian attempts to interfere and help the Trump campaign, and the Senate panel backed those findings this week.

Durham's scrutiny of the Russia intelligence is "like a proctologist," one source told CNN.

But it's unknown what Durham's findings or his end goals may be.

He could bring charges or issue a report, as Barr suggested in a recent interview with Fox News' Laura Ingraham, where he also called the FBI's Russia investigation "one of the greatest travesties in American history."

Though the Department of Justice has said Durham has the power to bring criminal cases and investigate using grand juries, it's unknown how extensively he's relied on grand jury subpoenas for documents or testimony -- especially now that federal grand juries across the country have largely stopped meeting. Many of his interview requests have been voluntary. Some witnesses refused to cooperate , such as when he was looking into former FBI officials' work.

Barr in his radio interview Tuesday said he's been "very troubled" by findings presented to him so far by Durham.

The comments from Barr came on the same day that the bipartisan Senate Intelligence Committee report bolstered the "sound analytical reasoning" behind the US intelligence community assessment that Russian interference in the 2016 election was aimed in part to help Trump defeat Hillary Clinton.

Trump has made frequent claims that the intelligence community and the FBI carried out a "hoax" by pursuing allegations Russia was trying to help him win and the President has called the investigators "human scum" for pursuing the investigation of his campaign. The Senate panel concluded that the Obama administration's assessment on Russian election interference was crafted without political bias, undercutting the President's claims that officials like Brennan and Clapper were improperly using the intelligence community to attack him.

Barr took the opposite position in his radio interview.

"I wouldn't use the word shocked," Barr told Hewitt. "I'm very troubled by it, but you know, I think the reason that we have this investigation is because there are a lot of things that are unexplained. And I think we're getting deeply into the situation, and we'll be able to sort out exactly what happened."