Federal prosecutors who are looking into the origins of the government's Russia probe have interviewed about two dozen people, suggesting that the inquiry is further along than previously known, The New York Times reported Saturday.

The prosecutors have asked witnesses about whether former FBI officials that have been frequent targets of President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE hold anti-Trump bias, former officials and others familiar with the review told the Times.

U.S. Attorney John DurhamJohn DurhamSteele Dossier sub-source was subject of FBI counterintelligence probe Barr's Russia investigator has put some focus on Clinton Foundation: report Top Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence MORE, who is leading the investigation, has not interviewed all of the FBI officials who were instrumental in opening the Russia probe in 2016, sources told the newspaper.

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Durham has reportedly not spoken with former FBI counterintelligence official Peter Strzok, former FBI Director James Comey James Brien ComeySteele Dossier sub-source was subject of FBI counterintelligence probe Judge will not dismiss McCabe's case against DOJ Democrats fear Russia interference could spoil bid to retake Senate MORE, former FBI Deputy Director Andrew McCabe Andrew George McCabeJudge will not dismiss McCabe's case against DOJ Graham: Comey to testify about FBI's Russia probe, Mueller declined invitation Barr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' MORE or former FBI General Counsel James Baker.

According to the Times, the moves suggest Durham may still be gathering facts before speaking with those key players.

Former CIA Director John Brennan John Owen BrennanJournalism or partisanship? The media's mistakes of 2016 continue in 2020 Comey on Clinton tweet: 'I regret only being involved in the 2016 election' Ex-CIA Director Brennan questioned for 8 hours in Durham review of Russia probe MORE told NBC News that Durham has expressed plans to question current and former intelligence officials including Brennan himself and former Director of National Intelligence James Clapper James Robert ClapperOn China, Biden is no Nixon — and no Trump The Hill's 12:30 Report - Speculation over Biden's running mate announcement Trump slams former intelligence officials to explain 'reluctance to embrace' agencies MORE.

The news outlet also reported, citing three former CIA officials, that the prosecutor is asking to speak with CIA analysts who were involved with Russia-related assessments and that some of the analysts have hired attorneys.

Attorney General William Barr Bill BarrFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Why a backdoor to encrypted data is detrimental to cybersecurity and data integrity FBI official who worked with Mueller raised doubts about Russia investigation MORE, who is overseeing the review, has said he wants to learn whether the collection of intelligence on the Trump campaign had a sufficient basis.

Critics view the Justice Department investigation as an effort by the Trump administration to undermine the intelligence community's findings on Russian interference in the 2016 presidential election.

Durham's review was not opened as a criminal investigation, meaning that the prosecutor is not able to subpoena witnesses or documents, although the Times reported that it is not clear whether the investigation's status has changed.

A law enforcement official told NBC that Durham has expanded his staff and the time frame of his investigation. A Trump administration official reportedly said that the probe is now going beyond Trump's 2017 inauguration.

The Times reported that at one point, Strzok, who opened the Russia inquiry after a tip by the Australian government, was the focus of the current review. Investigators reportedly asked about the tip, which said that Russia had offered information on Hillary Clinton Hillary Diane Rodham ClintonBloomberg rolls out M ad buy to boost Biden in Florida Hillicon Valley: Productivity, fatigue, cybersecurity emerge as top concerns amid pandemic | Facebook critics launch alternative oversight board | Google to temporarily bar election ads after polls close Trump pledges to make Juneteenth a federal holiday, designate KKK a terrorist group in pitch to Black voters MORE to the Trump campaign.

Durham also reportedly asked witnesses about Christopher Steele, a former British spy who had compiled a dossier of allegations about Trump that was used to obtain a warrant application that ended up permitting the FBI to wiretap a member of the Trump campaign in 2016.

One former official said that he rebuked the idea that officials sought to damage Trump's candidacy, the Times reported.

The person reportedly contrasted the public handling of the investigation into Clinton's emails in 2016 with the secret investigation into the Trump campaign before the election.

A spokesman for Durham declined to comment to The Hill on Saturday. The FBI also declined to comment.

Updated: 12:35 p.m.