By Katelyn Polantz and Kara Scannell, CNN

(CNN) -- Special counsel Robert Mueller's investigators were allowed by a federal judge to review years of Michael Cohen's emails and other online data from the time he worked under Donald Trump, according to newly unsealed warrants used in his case in Manhattan federal court.

In all, the prosecutors and FBI received permission from a Washington, DC-based federal judge to execute four search warrants on Cohen's two Gmail accounts and for stored data in his Apple iCloud account in July, August and November 2017 -- long before Cohen's office was raided in April 2018 and he pleaded guilty in an illegal campaign contribution and tax prosecution led by Manhattan federal prosecutors.

Mueller also received approval on two separate occasions to track the numbers of Cohen's incoming and outgoing calls.

The revelation gives new illumination to Mueller's work throughout 2017 -- before he had brought the bulk of his open criminal cases against defendants like former national security adviser Michael Flynn and a host of Russians for interfering in the election -- and shows how extensively Mueller had tracked computer data of those close to then-candidate Trump in the early days of his presidency.

The search warrants released Tuesday say that the special counsel's office referred "certain aspects" of its investigation into Cohen to the New York-based US Attorney's Office.

After pleading guilty in the Manhattan probe, Cohen also later pleaded guilty to lying to Congress in a case brought by Mueller's investigators. They have said he's been helpful to them, but have not revealed how so.

Mueller's search warrant justifications to DC federal court related to Cohen are not yet available.

The searches done by Mueller are described as part of the probable cause that led prosecutors to seek electronic phone and other data from Cohen in their illegal campaign contribution investigation, for which he was charged. Mueller also received warrant approvals on November 7, 2017, and January 4, 2018, to track the numbers of Cohen's incoming and outgoing phone calls and other phone call metadata. Mueller's team then handed over that data to the Manhattan federal prosecutors, and the Manhattan prosecutors also sought additional information filtered out of the Mueller searches.

At the time, Mueller's team was investigating Cohen for a host of crimes, including some for which he's not been charged, such as money laundering and acting as an illegal agent of a foreign government.

The documents released Tuesday, which number hundreds of pages, were released as a result of a ruling from federal Judge William Pauley partially granting a request from various media organizations, including CNN, to unseal documents related to the raid on Cohen's home, office and hotel room.

Cohen was sentenced to three years in prison by Pauley in December for multiple crimes, including campaign finance violations stemming from payments Cohen made or helped orchestrate in 2016 that were designed to silence women who claimed affairs with then-candidate Trump. Cohen is scheduled to report to prison on May 6.

Heavily redacted

The materials related to the campaign finance contribution scheme are entirely redacted in the documents, and there does not appear to be extensive justification that prosecutors have made visible to the public that describes their reasoning for looking at Cohen's phone and email communications.

Instead, in describing to a federal judge the probable cause they had to investigate Cohen's campaign-finance scheme, investigators write almost 20 pages of detail that are all redacted.

The Manhattan US Attorney's Office and FBI "are investigating a criminal violation of the campaign finance laws by Michael Cohen, a lawyer who holds himself out as the personal attorney for President Donald J. Trump. As detailed, there is probable cause to believe that REDACTED," they wrote to the judge.

Mueller's office was investigating Cohen for lying to banks, breaking foreign lobbying laws and money laundering, according to one of the search warrants.

Mueller's search warrants sought Cohen's emails related to his business dealings under a shell company used to cut hush money deals with women accusing then-candidate Trump of extramarital affairs, which Trump has denied.

Mueller's justification for those warrants were "several different courses of conduct by Cohen, including, among other things, false statements to financial institutions relating to the purpose of an account he opened in the name of Essential Consultants LLC and the nature of funds flowing into that account, and activities undertaken by Cohen on behalf of certain foreign persons or foreign entities without having registered as a foreign agent," an FBI investigator wrote to a judge, piggybacking on Mueller's pursuit.

This story is breaking and will be updated.