(CNN) Search warrant documents used by special counsel Robert Mueller's investigators reveal how agents zeroed in on potential criminal activity related to Paul Manafort's time as Donald Trump's campaign chairman.

The documents, used to obtain a search warrant in building the case against Manafort, were revealed in a court filing late Monday night. Manafort has pleaded not guilty in two federal cases, and the charges he faces do not include allegations about his time on the campaign.

The search warrant makes clear that Mueller is also focused on Manafort's actions connected to the campaign. The White House and others have repeatedly said that the investigation into Manafort concerns his activities before he joined Trump's team in 2016.

Investigators in a search warrant application last July told a judge in Virginia that they sought evidence related to Manafort's interactions with a Russian real estate magnate and were suspicious of possible campaign finance violations.

Specifically, the investigators sought from Manafort's apartment records "involving any of the attendees of the June 9, 2016, meeting at Trump Tower" and anything involving Aras and Emin Agalarov, an Azerbaijani-Russian billionaire and his son tied to the meeting, the 2013 Miss Universe pageant in Moscow and to a possible earlier unsuccessful attempt to build a Trump Tower in Moscow.

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